I just finished Discovery's third season as well and... oh boy. Minor spoilers for Discovery below.
So I'll just say I quite liked Discovery's first two seasons. It's been a while since I watched them, and I know they also had their issues, but looking down the list of episodes on IMDb I can see I gave most of them 6-8/10.
Now, the third season. The first two episodes were great and very promising (an 8 then a 6 out of 10), then it just descends into a pit of terrible writing, plot holes, stuff just happening without even a tangential scientific basis, constant crying from the crew, whispered dialogue, and motivational speeches crossed with a mawkish sentimentality. On a fucking science vessel. Just awful.
And the character trades this season were atrocious:
-We gained Book (the only good new character. Well, him and the cat), Adira (who has negative charisma, but more dedicated screentime in two episodes than most of the bridge crew has had in three years), and Vance (meh).
-We lost Nhan (meh) and Georgiou (good character, albeit given too many cheesy lines).
-We're probably losing Saru (they've got to be kidding, he solo carried this shit season).
-Oh and we've gained number one Tilly. LOL. An Ensign with no self-confidence, no training for command, who is both mentally and physically completely unfit to be in a position of responsibility on board a star ship. Promoted to second in command. Makes total sense, nice writing guys :)
I ended up giving half the episodes 2 or 3 out of 10, which is just abysmal, especially for sci fi. I can look past a lot of issues for sci fi, because it's my favourite genre, especially space-based stuff. But by the end of this season I just want it cancelled, especially now it looks like the best character by far (Saru) is being written out and we're going to get Star Trek: Burnham on steroids in season 4. I actually want a Star Trek show to be cancelled, that's how bad it's gotten. I never, ever thought I'd say that.
The only saving graces of season three were the first two episodes and the Mirror Universe ones in the middle, which were a welcome relief. But they just made me want a Mirror Universe Star Trek series with new writers, instead of more Discovery.