I feel like the hype around the MCU just completely died after Endgame and despite all the new stuff coming out, there's just no hype around future releases.
I think endgame was such a huge thing with its massive buildup over 20-something movies that the new movies like eternal feel smaller and lacklustre in comparison. Also might be that externals is less well known? I didn’t know about Eternals at all until I saw the trailer and then looked them up after.