Iirc there are some that are literal direct ripoffs (exact same sets with a ELGO or some obvious ripoff brand) that appeared at a time, and were pretty obviously run off of a Chinese Lego line (I believe Lego got them shut down by winning a copyright case in China).

The quality of off-brand is way up in the last 20 years but it’s still not the same; they run the molds way too long.