Here are my honest thoughts about Genshin Impact 4.0. Fontaine is beautiful, but the under water areas are quite boring for combat focused players from what I can tell. The quests feel more of the same, but the Archon quest for 4.0 seems better than Sumeru currently. I think that Genshin will keep being a popular game people can explore in... but if exploring isn't exciting to you, it may be time to take a break.
I don't hate 4.0 or anything. I am just not really engaged with the content or having much fun.