Similarly I can see where you come from, though truthfully I think SM Ash is no more flanderized than he was in XY, maybe less so. Flanderization isn't just making a character goofier, it's simplifying a character to certain defining traits.
XY Ash was still simplified, but more to his 'winner' qualities than his butt monkey ones, being suave and heroic the majority of the time, just because it was a positive trait doesn't mean it's flanderization any less. I do understand why some like XY Ash because him gaining such prowess feels cathartic to his development (that was overlooked in BW) but I feel they went too far and made him a bit bland, and the relationship with the XY lot I found even less depthful because of it.
Besides that I think SM Ash still regularly conveys a lot of XY Ash's best strengths. He can be equally insightful and badass when the time requires it, almost every episode in fact, just it's more a 'Let's Get Dangerous' transition, with him being more dizzy and buffoonish off the clock but knowing when to get serious. The animation is a bit overdone (though I'm used to deranged anime/animation so I suppose it's less effective on me) and his butt monkey qualities are sometimes exaggerated, though more in early episodes where he usually suffered more over everyone else, later on the limelight and slapstick is more indiscriminate. I kind of prefer this setup with everyone having strong and buffoonish qualities, it makes them feel fully dimensioned in spite of the cartoonish output (or sometimes because of it), while previous series like DP and XY maybe tried to make too much separation in super serious and dignified characters vs incompetent comic relief ones, which I thought made for blander characterisation.