There’s lots of answers to this depending on taste, but you also get into arguments about whether such and such is space opera or planetary romance. Children of Time is hard SF the way a reader from the 1960s would have understood it.
I second this -- but, at the same time, it's such a shame that Tchaikovsky hasn't written anything else worth a damn, despite writing something like three novels every year!
His two most recent, Shroud and Service Model, are bloated, uninspired, and borderline unreadable. I guess he's now subject to that curse of established authors, where editors are scared to mess with their manuscripts and trim the fat.
Project Hail Mary is light reading sci-fi. Which is fine, I enjoyed it, but if you are looking for something meatier, covering broader themes and character development, here's some other recent stuff (there's a lot of old stuff covered already in other comments):
Stories of Your Life and Others; Exhalation (Ted Chiang) - both are short story collections vs novels, though
Dissolution (Nicholas Binge)
Too Like the Lightning (Ada Palmer) and sequels (wordy, philosophical, interesting future society)
Tell Me an Ending (Jo Harkin) - more near-future and grounded
I second Daemon as an excellent sci-fi. I also really enjoyed Project Hail Mary and thought the characters weren’t too bad for a sci-fi.
Daemon isn’t about a rogue AI in the sense it was designed that way. Also you need to read the sequel “Freedom” to really get the true sci-fi philosophical message.
I personally enjoyed the sequel Freedom because it really explores the idea of a crypto-DAO like society that embraces human nature to build a more sustainable and fair society. It was ahead of its time as I don’t think DAO’s had been created yet.
Suarez’s later books also build on the themes in interesting ways.
Yeah I was going to say the same thing. Pandora's Star/Judas unchained is the best scifi I've ever read. Peter F Hamilton's worldbuilding is unmatched.
scalzi is mil-sci-fi, which I also enjoy, but not man vs nature conflicts like weir writes about (even Artemis is largely about solving physical problems even if they arise from interpersonal conflict..)
If you define quality as "layered and meaty" there are many much better books.
Roadside picnic (and its less Russian counterpart, Annihilation), left hand of darkness, Solaris are all excellent.
If you want culturally influential, surely Starship Troopers, Stranger in a Strange land, anything by HG Wells, 1984/Brave New World, Frankenstein (duh)
The characterization in Hail Mary is just so damn weak, even space opera stuff like Bujold
