Ashes could have been more interesting if their use was more varied. There are some that do have passive or latent benefit to the player that goes beyond their combat usefulness, but even those most of the time get involved into the combat, which is what "ruins" bosses because it changes the dynamic completely, presumably in your favor, often against you (boss movesets are tuned for a single target the second their attention moves between you and the summon and back to you it results into a complete mess at times).
In the open world, i found ashes to be quite ok. They can help you clear the boring stuff faster which isn't bad. If you weren't spending the FP on ashes you'd be spending it on spells to clear out hordes of mooks so what difference is there (builds that don't use spells might get even more milage out of this). Whenever i'm farming i always use ashes because why wouldn't you. If you count spells and weapon arts, ashes in themselves aren't really that problematic it's only against bosses that they become a problem because of how they can confuse the AI.
Outside of the niche uses i just mentioned, i never used them because of course i want to do everything "fair and square" but i don't mind the attempt at trying something "new", even if it could have been done better.
Elden Ring actually sort of shares something with Dark Souls 2 in how both games tried to do a lot of new things, but sometimes it felt they didn't think everything through. So on one hand you have the added novelty factor, on the other you can't help scratch your head and wonder what they were thinking.
BTW, speaking of Dark Souls 2 and things "intended" by the developers, i'm reminded how everybody absolutely hated those extra areas in each of the DLCs (Frigid Outskirts in particular) that were CLEARLY intended for co-op but everybody did them solo anyway (and then bitched about them endlessly). Sure, maybe forced co-op shouldn't be a thing in those games, but still, they wanted to do something, why not do it their way? I did all those areas solo myself but i didn't complaint since i knew what i was getting into. Those areas is what gave me the idea the double and tripple bosses in Elden Ring were sort of intended to be fought with spirit ashes. I did them all solo, but the way people complained about them (to the point FromSoft felt compelled to nerf the AI, a HUGE mistake in my opinion). If you found them so irritating, why not do it the intended way?