Is anyone else in the same situation (creator's block, lack of progress, frustation)?
Only about 99.9% of everyone who has ever used some iteration of RPG Maker. Understand I am not saying this to dismiss you, but you've essentially just described virtually every RPG Maker user ever. I sincerely doubt you can find anyone here who hasn't gone through periods of exactly what you're talking about.
& to be blunt, most advice you could be given on the subject, amounts to little more than platitudes when it comes to this sort of thing. There are only two options, either you keep going, or you quit.
If you have completed a game or games, can you give me some advice on how you created your game(s)?
If I had to put a number on the number of people who have actually completed a game with any iteration of RPG Maker, I would say it's about 1% of the total user base. & of that 1% who have made a game, I would say that 90% of those games aren't anything more than shovelware slapped together "hey look I made a video game", whose creator never made a second game because they realized how much work actually goes into making a game. There is a reason why RPG Maker games have the reputation that they do.
I am not saying this to discourage you, merely putting things into perspective. You should understand that most people pick up a Unity, a GameGuru, a GameMaker, or an RPG Maker dramatically underestimating just how much of an investment of time & energy it takes to make a game worth putting your name on. Which is why the overwhelming majority of people when they encounter what you are talking about, quit. While those who push forward, have to make a great deal of personal sacrifice, to make something worthwhile.
For example, on my project I have affectionately dubbed "the monster" (not the title), version whatever the hell I am up to at this point.
I started with VX Ace, & I am honestly not certain how much time I put in on that iteration. Then I picked up MV through Steam, & transferred the project over to MV, rebuilding the whole thing from square one. Steam tells me I've topped 3200 hours on the program this month, which is equivalent to working a full time job for a year & six months. That's also not factoring in time spent brainstorming with a notepad & pen, or time spent in secondary programs like GIMP.
If I had to guess I am sitting somewhere between 4,000 & 5,000 hours of time invested in this project grand total; & I MIGHT be at beta testing phase for it before I hit the 5,000 active hours in MV on Steam, which will probably put me over 7,000 hours total time investment.
Advice, tips, tricks? Sure between everyone here, an encyclopedia could probably be written; but at the end of the day those are about "how do I do X?" which isn't really what this is about. You're asking how do other people stay motivated when they hit the wall.
Why do I keep working year & after year, carrying around a notepad & pen brainstorming random details about stories, classes, characters, world lore, etcetera; chipping away at that monolith? Because I think it's worth it, that's it. Everything else is just superfluous details that are entirely project dependent.
Anyone who make games solo, how do you overcome your weaknesses? (bad at art, bad at math, no scripting knowledge)
Either learn to do those things, or stop being a solo. "I am bad at X" is simply an excuse.
Whether it's purchasing what you need, hiring out what you need by commission, or joining a team of people who can do what you can't, you find people who can get you what you need. Or you teach yourself to do what you need to do.
One involves greater expenditures of money, the other involves greater expenditures of time. If you aren't willing to do either, then discard whatever it is you're trying to do, & create a new plan that doesn't require what you can't produce or procure.