I liked him, in fact this is maybe the first series I considered Ash the main draw appeal, though maybe because I simply have a soft spot for those 'warm hearted kooks with a deceptively brilliant side' archetypes.
Ash felt very fallible in this series, the writers maybe overdid the whole slapstick butt monkey angle at times, but I don't specifically mind a character getting crapped on, I like an underdog who has foibles but can in some way still vindicate themselves (if anything I wanted more cases another character got 'loser' moments, not out of vitriol, I wanted more reason to sympathise with them, singling out Ash too often made some of them boring and over complacent). While a rather different take on him, I think SM Ash well personifies many traits fans start to relate to his tenure in the show, this nomadic over-enthusiastic weird kid who at face value fails at everything related to his goals but still somehow accomplishes everything else and comes off as strangely brilliant.
Ash has plenty of agency this series, like he can be put into nearly any episode and drive it in some amusing way, a far cry from his blander XY and even BW self. He doesn't even need to battle to be effective (though while his skills are underplayed this series, they're still decent enough to gather he's competent at it), we get eccentric moments of insight like him going Jane Goodall with some Passimian or playing host for a Morelull.
Ash also immersed pretty well into this series' universe, he had good chemistries with several of the students and worked as a catalyst character pretty well. I could argue the school should have felt like a far more important element to his role, but it was undeveloped all around so that's not as much his fault. I do like this was maybe the first series he had to significantly alter his direction rather than just do the same thing in a different backdrop. We see him get into situations he is completely out of his element in, like having to be more proactive for a companion with a serious problem or moments of being crafty which don't just concern strategising a battle. I love the humility with this Ash and yet still retaining the same optimism and willingness to give anything the old college try.
There are some downsides I admit, again the butt monkey/over the top deformed faces moments are a bit oversaturated while the school trials are undersaturated, along with his team and battle skills (though I do appreciate the level of legit training his team have done this series, maybe the one time legit earning a move has stayed on level with the number of plot armour moments). Also Ash has had odd moments of taking on traits or flaws for the sake of a plot that don't really stay consistent to his character (he REALLY shouldn't have to be taught to be more acceptant of a Pokemon leaving him, especially since even this series has been consistent with that element in other episodes). But overall I think the good far outweighs the bad, this Ash has been very charming and rounded, hopefully next series will fine tune the bugs that remain while keeping the improvements.