I trawled through AniList for the 2020's and here are some I enjoyed that I don't seem to see people mention very much. Ten in no particular order:

1. Brave Bang Bravern! - ridiculously fun show. Takes the piss out of every other mecha show that comes before it.
2. Bofuri (and season 2) - a VRMMO-type show that never takes itself seriously with some really cute moments
3. I've Been Killing Slimes for 300 Years and Maxed Out My Level - A "slow-life" isekai filled with cute characters that just struck the perfectly relaxing mood for me. Season 2 coming next year.
4. Love After World Domination - A cute romcom between the red ranger and one of the evil organization's leaders. I will always lament the early cancellation of this manga, but the anime was great as well.
5. Campfire Cooking in Another World with my Absurd Skill - Just a fun, laid-back isekai about cooking with zero stakes (and a really fun OP).
6. Reborn as a Vending Machine, I Now Wander the Dungeon - Most people dismissed this show based on the title, but for those that actually watched it, it was surprisingly good. Not amazing...but definitely fits the underrated moniker.
7. Endo and Kobayashi Live! - A villainess series that is just full of fluffy romance. If you like tsunderes, then this is right up your alley.
8. Chillin' in Another World with Level 2 Super Cheat Powers - A series that starts with a painfully generic episode 1 before revealing in episode 2 that the actual genre of the show is romance instead of any kind of power fantasy with no harems allowed. A lot of people dropped it after just the first episode.
9. TSUKIMICHI -Moonlit Fantasy- (and season 2) - Not sure how underrated this is, but I really enjoyed it, even as a source reader. I feel like this series has a small but dedicated fan base in the West.
10. Level 1 Demon Lord and One Room Hero - This is a very silly fantasy show about a hero that has let himself go in retirement. As the show goes, it builds to some real touching, emotional stuff, but you just need to get through some fan service on the way there. Way better than I thought it was going to be.