Still using tons of ES5 constructs has at least the following advantages:
1. Porting MV plugins into MZ don't have to convert them into ES6 to be consistent with the default MZ codebase, and
it's a major factor for many MV plugin developers planning to do so
2. Those not being familiar with/not preferring ES6 don't have to learn/work with it, and
the number of such MV plugin developers' better not to be underestimated
Whereas really following the ES6 standard has at least the following advantages:
1. New RM plugin developers(i.e., those never workjed with MV before) not being familiar with ES5 don't have to learn it, as
there are quite some JavaScript programmers(hobbyists or not) picked up JavaScript after ES6 becomes the mainstream
2. It allows the RM codebase to improve more quickly and keep closer to the mainstream when a new RM comes and thus encourages more new RM plugin developers to join the RM community, as sticking to ES5 for the advantages it gives for
THIS MAKER can lead to the subsequent RM versions
LOCKED INTO ES5 for a long time(
the later the switch the harder and more costly it's in general), causing fewer and fewer new RM plugin developers to join(being consistent with the default RM codebase is a major factor for many plugin developers), due to the fact that ES5 will only become more and more outdated, eventually causing the later RM versions to become too dependent on existing RM plugin developers, which can be serious troubles if many of them decide to leave RM, and
this will happen eventually
But first, let's divide the potential MZ plugin developers in the following groups:
1. MV plugin developers already being familiar with ES6 and preferring ES6 over ES5
2. MV plugin developers already being familiar with ES6 but preferring ES5 over ES6
3. MV plugin developers not being familiar with ES6 but is already learning it
4. MV plugin developers not being familiar with ES6 but isn't learning it
5. New RM plugin developers already being familiar with ES6 and preferring ES6 over ES5
6. New RM plugin developers already being familiar with ES6 but preferring ES5 over ES6
7. New RM plugin developers not being familiar with ES6 but is already learning it
8. New RM plugin developers not being familiar with ES6 but isn't learning it
From the following 3 dimensions:
1. MV plugin developers vs new RM ones
2. Already being familiar with ES6 vs not so
3. Preferring ES6 over ES5 vs the opposite(Of course there are plugin developers being okay with both)
Now let's think of how each among the 8 potential MZ plugin developer types will generally react to MZ still using tons of ES5 constructs(
those okay with both ES5 and ES6 likely don't care about this one bit):
1st type: They'll likely treat this move as a massive disservice, as ES5's very, very outdated in the JavaScript community(but still far from being totally irrelevant though), so most JavaScript programmers should be familiar with ES6 already, meaning that still using tons of ES5 constructs is prioritizing the minor group of not being familiar with ES6 over the vast majority of the JavasScript programmers.
2nd type: They'll likely be okay with this move, as porting MV plugins to MZ can become easier, simpler and smaller tasks when the need of converting those ES5 codes into ES6 codes reduces significantly(being consistent with the default MZ codebase), and sometimes direct prototyping does make more sense than using classes, and most importantly, those preferring ES6 over ES5 can still write their MZ plugins in ES6, if the use of ES6 over ES5 means so much to them that they're willing to pay the cost of writing codes not being consistent with the default MZ codebase.
3rd type: They'll likely be so mad that some of them will probably just "rage quit" by cancelling the MZ pre order and never caring about MZ ever again, as it's only natural(but still not fully justified) for them to feel that their efforts on learning ES6 just to adapt to the MZ codebase's all wasted, even though it's crystal clear and obvious that it's not wasted at all, as becoming familiar with ES6 gives them a vast advantage as JavaScript programmers.
4th type: They'll likely praise MZ for making this move to take their needs/preferences into account, as being familiar with ES6 still demands a nontrivial amount of work(even though even a bad junior programmer like me can do so within just weeks), and some of them may have no time to learn it but still want to release MZ plugins as soon as possible(it really depends on their situations), which can cause troubles for them if MZ really follows the ES6 standard and they need/want their codes to be consistent with the default MZ codebase.
5th type: They'll likely feel that MZ prefers existing MV plugin developers over those new to RM, and perhaps similar moves will be made for the next makers as well, as it's hard for them to fathom why MZ made such a decision otherwise, especially for those not being familiar with ES5, so some of them might just cancel the pre order and even conclude that RM's going to be deprecated in the foreseeable future, all because of refusing to update the codebase to the mainstream ES6 from the outdated ES5.
6th type: They'll likely think very similarly to the 2nd type, except that porting MV plugins to MZ won't be their concerns, so they're unlikely to praise this MZ decision as much as some of the others.
7th type: They'll likely think very similarly to the 3rd type, but maybe even more so, because unlike the 3rd type, they won't get the benefit of having less work to do when porting MV plugins to MZ.
8th type: They'll likely think very similarly to the 4th type, but perhaps even more so, because nowadays it's quite hard to find a ES5 codebase to work with, and MZ will be a blessing to them as they aren't familiar with ES6 and aren't going to learn it, so it's normal(but still not certain) that they'll be some of the biggest supporters of this MZ decision.
So, if still using tons of ES5 codes is indeed a wise decision in MZ, it means:
1.
Currently, the 2nd, 4th, 6th and 8th types, and those being okay with both ES5 and ES6 will be the majority of potential MZ plugin developers, despite the fact that most JavaScript programmers in the JavaScript community are familiar with ES6 and some of them aren't even familiar with ES5, meaning that MZ is a niche even in the programmer/programming perspectives
2. For the whole RM franchise,
it's more important to prioritize the existing RM community programmers, especially for those wishing to stick to outdated practices, than attracting new programmers into the RM community, especially when some of them can't/won't work with those outdated practices(despite the fact that existing RM community programmers will eventually leave RM), and this can be due to the fact that
many MZ users will be existing MV users as well and vice versa, thus the need of porting MV plugins into MZ will be large enough to place the need of "removing the work for converting them into ES6 codes as well to be consistent with the default MZ codebase" into a very, very high priority
Of course, I don't have the numbers while both Degica and Kadokawa definitely have, and I don't know how many new RM after MZ will be while they might already have plans on it, so I'll refrain from judging further whether still using tons of ES5 codes is indeed a wise move in MZ
;)
P.S.:
Not all hobbyists will remain hobbyists forever, so the average rate of change from hobbyists into professionals is also a very, very important number when evaluating whether this MZ decision's a wise move.