There's an art to being a "busy" bassist. No One Likes A Busy Bass Player is the mantra, and there's a lot of truth to that. However, when I saw Entwistle (completely different style to Gene, of course) he was the very definition of "busy bassist" yet he never seemed to be overplaying.
Gene's just very melodic, I guess it is busy, but it never struck me as overplaying. And yes,some of the early Kiss stuff is very Stones based rock 'n' roll.
I think the reason Kiss in general and Gene in particular got dissed in the '70s was that they were an easy target at that time because of their stage show and makeup. The prevailing mindset that I remember from back then was that bands were supposed to GROW and PROGRESS musically. If your first album sounded like Kiss your third should sound like Blow By Blow. Or, if you were a Canyon Rock type band like The eagles or firefall, that was permissible too. Not that there's anything wrong with those styles/bands, but that predjudice is what I remember from back then.
When I look at YouTube clips of early live Kiss, I'm struck by how tight they were, even if without taking into consideration that they were putting on a show too.
Re steady 1/8th notes being trendy in the '80s, yeah, that's true. I think it started with Cliff Williams, nobody plays straight 1/8th notes like that guy! I do feel that rock bass playing in general has become very basic and tame since the '80s.