Someone said that the biggest mistake was selling Segwit as a scaling solution, I believe that’s true. If it wasn’t sold that way, I believe it would have been activated with no drama.
but SegWit was a scaling solution, it increased the maximum capacity by 4 MB weight which currently is capped at 1.6 MB size. it also doesn't stop there, it paved the way for more scaling to come. for example implementation of Schnorr using SegWit is a lot easier and doesn't need a hard fork and is another capacity improvement.
it also made Lightning Network a lot easier by fixing some remaining malleability issues. which is another scaling solution.