So while it isn't claiming to be ready, their content does not tell otherwise. Yes, the version is 0.3, but Neovim is at 0.9.
I would argue that that's a fault on neovim's side; I'm sure there's a reason, but I would call it 1.x software.
duck and run
That would be nice but in reality it's such a tricky and subtle problem that nobody does it perfectly. All the operating systems and browsers are buggy in different ways, nevermind anything with smaller budgets. The deeper you get into proper text handling, the more you will realize that nobody has solved it.
Displaying text is an even deeper issue and also broken, the further you go from latin alphabets.
Referencing MS-DOS really takes the cake though. The Unicode standard wasn't even released until late 1991. They're still updating it even today, because it's a lot of work to handle international languages.
It's certainly an issue, especially for non-English users, but it doesn't "disqualify the whole project"; it just means that's not what they're prioritising at this time.
https://github.com/lapce/lapce/issues/2244
https://github.com/lapce/lapce/issues/1094
https://github.com/lapce/lapce/issues/1689
https://github.com/lapce/lapce/issues/2731