I definitely am not against Arkham’s many expansions. I love that game most for its intense variety, and every expansion makes that better - in isolation. You just really shouldn’t play with all of them at once.
And I agree that Eldritch does not obsolete Arkham. There are things I absolutely prefer about Arkham, like being able to get around the board quickly, and having dice pools that seem balanced for the success mechanic. And the agenda is also very different - you have to close gates to win and cull monsters to keep terror under wraps, whereas gates and monsters in Eldritch are problematic but you are frequently not in a position to actually advance towards victory and keep them under wraps.
I suppose Eldritch is overall a better design but I would happily play both.