The new features with sub classing is amazing and it adds some extra theory crafting for builds. The issue that i am noticing is that it adds a lot of extra power (either that's dps or more uptimes) and as a result it makes old content way easier (which became way easier when arcanist came) and people who will decide not to use sub classes be underpowered.
I am supporting the sub classing system but if only it's balanced. In addition you really need to balance old content, for example add hard modes in craglorn trials, increase their health pool, damage they do, etc.
When i started doing trials which was around when kyne aegis came out (i remember it was the nb meta back then) content felt way more balanced and when you accomplished a trifecta it felt that you earn it nowadays ever person has almost every trifecta done because arcanist is just the best and easiest class to play (high dmg, high survivability, ease of use). The common logic should be if you want to play something that's easy you should be sacrificing something else (either that's dps or survivability or whatever that might be).
My point is i would like content to feel as they did back in the old days and not everybody be able to achieve some stuff because they have easy mode enable, you should work for some stuff. In order for this happen there need to be some balance changes to the classes themselves and to sub classing now and in addition balancing old content (craglorn was an example and it's not the only old content that needs balancing - i would say from rockgrove and before content needs rebalancing).
Put the effort to make the game more fun for casual people and for people who like to have a challenge.