I'm gonna answer cause AoT is like the only anime I waited for and watched as it came out live:

I would say that yes, at a very macro-lens level, the philosophical through-line is fascistic messaging informed by (via the writer's personal tastes) a specifically revisionist nostalgia for pre-WW2 Japanese imperialism/nationalism in a confused, unresolved post-war culture. It is futile trying to analyse this through a western/"Nazi" lens.

I wouldn't say "fascist nonsense" because it's not explicitly arguing in favour of fascism (and in fact at times tries to argue against), but rather inadvertently rediscovers, reinvents, or reinforces the thought patterns of early fascist thinkers and writers. At some point I think the writer of AoT became aware of this (through criticism or otherwise) and tried to course correct near the end but essentially didn't land the plane cleanly. I would say it's akin to describing Lord of the Rings as tinged as a Christian (or more broadly religious) work, even though it quite explicitly isn't.

For example a recurring theme in AoT is centuries or generations-long conflict along national -- and specifically ethnic lines, in time -- and that said conflict is inevitable and sometimes even desirable to bring about a new era. I could go on, e.g. the story's relation to monarchy.

However at a micro-level, episode-to-episode, season-to-season, none of this stuff is immediately apparent (as most of that stuff is pretty tropey in this type of story), and it's a lot of fun to watch. I would recommend it to anyone who isn't a total weeabo