There are a few similar open source projects, like Tic-80 and Liko-12. Both can be programmed with Lua, but Tic-80 can also be programmed with others like Javascript and Wren and the porting process can be fairly simple.
Brief selection of some projects things that I personally enjoyed[1]
And they all have one thing in common: They hit the limits and were unable to progress.
I remember when the first thing you had to do in order to program a videogame was creating your own TIFF or BMP parser. That's ok if you enjoy that sort of thing, but it gets in the way when what you want is a working videogame, not a tech demo. That kind of limitation, frankly, sucked.
On the other hand nowadays the problem is the opposite: there's so many ways to do stuff. So many options. Which engine. Which language. What graphics pipeline. Which Entity-Component System, etc.
The trouble is that we are back to the previous problem. The tech decisions get in the way of the creative process.
What Pico8 does right is limiting the amount of tech-related decisions you have to make. That frees mental cycles in order to be creative and build something that works. I know from the get go that I've got 8x8 16-color bitmaps, and that's it. No time wasted parsing TIFFs, and also no time wasted choosing tech. You start and go.
All that said, I don't think Pico-8 is for everyone. If you feel restricted by it, perhaps you will be more comfortable with other engines. I program games as a hobby an I am very limited on the amount of time I can dedicate to it. I tend to make small 1-evening prototypes that are never finished. Pico-8 is awesome for that. It's definitely awesome for me, at least.
How is it a tech-related decision if I want to add another sprite, but can't, because PICO-8 decided for me that I'm only allowed to have a specific amount? It's completely arbitrary and literally stops a game's development! That's not what a game development tool is supposed to do!
A screwdriver isn't "good" at putting nails down. It would be pointless to say that it's not a good screwdriver because it doesn't drive nails. Pico-8 is like that. It only allows a certain amount of everything: sprites, sounds, colors, even program tokens.
I must point out that it is possible to drive a nail using a screwdriver. You hold the screwdriver from the metal end, and repeatedly hit the nail head with the handle. It's a bit awkward. (But also sort of impressive. Like the people that do 3D stuff with Pico-8).
There are options out there to go around most of the limits if you really want to. You might have to sacrifice something. You need to be creative, the same as with the screwdriver. I actually enjoy that.
More like lovely schizophrenic tool. Not everyone need/want to get lost in a tonnes of features.
Being Nim-based means the result can be compiled to C or JavaScript, so it can run at native speed or in the browser.