Not just aliens. Alien, aliens.
While hardly a first for Star Trek, it's always a treat when alien-looking, and alien-acting, aliens show up.
The season had a good pace, but in my heart, I wanted more. I really feel like it would have made a fun (if not nerdy) season if we had a few more episodes decoding mysteries and getting to know this new culture and species.
I felt the same way, at first. Then I realized that we have other things in the Trek canon that asks as much suspension of disbelief:
Edit: my head-canon for the weirdness of Disco's first season is that they really wanted it to be the start of a Kelvin-verse TV reboot, but were coy about it.
Edit 2: I forgot about the Kardashev Type 3 civilization of robots living just outside our galaxy, that will turn the Milky Way into a lifeless wasteland if anyone so much as prank calls them. But they made their digits really hard, but possible, to find.