A lot of things are social vanity games.

However, toy projects are not.

Making your own toy LLM is incredibly important if you want to work on LLMs.

Making your own toy compiler or toy language is incredibly important if you want to work on such things.

Knowing C and some basics of assembly are incredibly important if you want to work in any performance critical problem domain. You will need to go through some toy projects to understand this well.

Some problems are technically difficult enough that they require practice. Iterations of work that are throw away to develop skill. Some require quite a bit of practice. If the problem domain which interests you is as simple as just making a sandwich, then ya just go make the sandwich. But some things take many hours of practice to grok and be effective at, sometimes years of practice. A surgeon doesn't just immediately start doing brain surgery. 

Personally, I think you always want to spend invest a good amount in technical practice otherwise you are in the rat race chasing all the low hanging fruit with the mass crowd. Like gaussian splats come out and someone with little technical practice might just try to make another web front among potentially dozens. But someone well practiced with graphics programming could try to make a new rendering approach that is faster than all the others, of which there probably are few attempting that.