"Polyglot" refers specifically to language though. I've always taken it as someone being fluent in > 3 languages, following biligual and trilingual.
Based on your proposed alternatives, you're likely thinking "polymath".
Yes that’s what it is, thanks for noticing
So what exactly is wrong with these words in your opinion?
The blog author speaks around 15 languages competently and he reads in about 15 more. Here's a 2 hr long interview with him where he touches on this topic: https://azeletmegminden.hu/040-sajo-tamas-podcast/ (in hungarian)
I would like to propose just saying “well rounded”, or “multifaceted”.
Its almost as bad as people that care about Mensa.