I would like to nominate A Memory Called Empire by Arkady Martine.

It’s a fantastic entry into the genre. Interesting future human cultures. The world feels very fleshed out and unlike anything I have read before. It plays with the concept of what an “alien” even is.

I love pretty much all of his books but this trilogy was truly epic.

Basically everything by Adrian Tchaikovsky But specifically Children of Time series. Humans are essentially the “ancient” alien race. It’s a unique spin on it.