Except that at the end of COIE, all the destroyed earths were restored in the new Multiverse. We didn't see Earth 90 among them but that doesn't mean it wasn't restored either. Marc Guggenheim gave an interview where he said that all the destroyed earths were restored - in fact that was a stipulation on WB's part that they had to make it clear on-screen that all those other universes/stories were still out there.
And frankly, the Arrowverse has done nothing but respect the 90's Flash TV show. Its given it a new lease on life. JWS is a household name again, and has been rediscovered by a new generation of fans (including me). The CW's Flash is arguably a spiritual sequel/successor to that show.
Agreed. I thought it was fitting that they had the 90's Barry be the one to enact that scene. Arguably, JWS's Flash is closer to the classic Pre-COIE Flash than Grant's version who is more reflective of the modern Post-Rebirth incarnation.
Everyone calls it the Arrowverse, including the people working on all the shows. Its also about respecting Arrow and Stephen Amell for kickstarting this universe (and arguably rejuvenating superheroes on TV in general).