People who only played the exact linear story progression were saying that. Which is nuts. You can’t play The Witcher 3 story progression that way, either. Honestly, it felt like it was people who wanted to bitch about UBI selling XP bonuses and looking for straw man reasons to complain about it.
There’s so much to do in the game and so much to see that there’s zero reason to buy any XP boosts whatsoever. You’re going to be struggling as it is to keep your gear within arm’s length of your level because the game honestly is so generous with XP requirements/level even into the 30s and 40s.
Most reviews either don’t mention it at all except in passing that it’s available. Very few call it a requirement to enjoyment.