[candleknight]

> I've seen excellent competitive programmers end up being mediocre engineers

I've seen the opposite. I know many extremely talented competitive programmers (IOI, CCO, USACO platinum, Codeforces grandmasters, ICPC, and the list goes on) and they are all excellent engineers. It's not about having a wealth of knowledge about DSA (although this occasionally helps, depending on the type of work) or competitive programming itself, but rather the skills it teaches. They all know how to learn new things very quickly and thoroughly, and it goes without saying that their general problem-solving skills are incredible. They've interned at companies like Snowflake, Google, Jump, Citadel, Jane Street, Waabi, Uber R&D, DataDog, SingleStore, etc. (all before or during their 3rd year, which is practically unheard of for "normal" students, especially during the tech recession) and have consistently received the highest performance grade (our co-op program requires employees to give them a rating on a scale from 1 to 7). There are also a few I don't know directly who are in fact working on things like Bard, or have founded their own companies (TabNine was one of them IIRC).