Sorry, but it is not clear to me. Lezer obviously works in the real world, as codemirror is quite widespread (integrated in chrome dev tools for example).
And since I use codemirror anyway, it might make sense to also use lezer, unless there are downsides I am not aware of.
I think Lezer is great if there’s a parser for your language, or you only need to support a few languages and you have time to build grammars yourself.
When you need to build a general tool that supports a ton of languages, that’s when Lezer doesn’t fit as well since there just aren’t a ton of existing grammars out there.
