I was playing at the casino last night and the dealer was constantly doing 2 things:
1) Dealing cards in a way that made them flick up slightly so that other players could catch a glimpse.
2) Dealing cards in a way that made them completely flip over and get exposed.

Now we have a rule at my casino that if 2 cards get exposed preflop, then it's a misdeal. With this dealer, literally 30% of hands resulted in a misdeal and it was slowing the game down a lot.

What's even worse is that literally every hand, I could see other people's cards because of the way he pitched them, which made them slightly flick up in mid air. I would sometimes see my own cards before even touching them. Sometimes I'd just see like a red picture card, but other times, I'd be able to predict the exact card and suit.

This is an uncommon occurrence at my casino, but it's certainly happened a few times before.

What can I do when the dealer is this incompetent? And what do I do when I think I can see someone's card flick up, but I'm not 100% sure what the card is?

Talk to the floor away from the table.

"Dealer that card flashed"

If you're certain you should call the cards while they're in the air. Then I'd talk to the manager and if the problem isn't fixed I'd take a stroll when that dealer sits down.

Most of the time, the best I can see is a "red picture card" or a "black low card".

One time, I tried calling it out by saying "I saw that, it was the 6 of spades", only for them to flip over the 8 of clubs instead. So that was a bit embarassing on my end.

What would you do when you only see a glimpse and aren't 100% sure?

Say what you saw. 'That's a red picture card' is important enough by itself. There are very few things that make me hot at a poker table but a dealer that can't correct their pitch is one of them.

It doesn't matter if you know what the card is.

All that matters is that someone might know what the card is.

Presumably, this dealer is able to pitch properly; I think all casinos are going to employ only people who have been trained and/or auditioned for the job.
If he isn't cheating (low likelihood), then he is getting lazy (high liklihood). Management needs to get on him to get back to form, or coach him back.

When I played in Melbourne years ago they had a new batch of dealers come in who knew the rules well but some had literally never pitched a card before. They had to ask the floor how to hold the deck. Maybe they came in from Sydney where they slide the cards out of a small shoe instead of pitching, or maybe the training was just lectures. I don't know. It's a weird world down there.

In any case, tell the floor away from the table about the issue. Maybe catch the dealer away from the table as well and tell them that the flashed cards are a big disruption in play and that they should get some tips from a good dealer on how to do it right.

Another possibility is that the dealer is normally fine but is currently injured.

Yep and yep. Aside: Many Seattle-area floors will ask you, "So what card did you see?" I usually say "Black spot card" or whatever, but this is silly of them.

First, if the card flashed to someone else, I may have seen only the back. Still, I saw it flash.

Second, it's hard for me to angle as long you commit to replace the card regardless of what I say. But it's easy to angle (at least once) if you make me describe the card and only replace it if I'm close to right . "Optimal" angling (in most games) is to say, "red ace" or perhaps a spot card like a 2 or 3 in 2-7 lowball.

(Not advocating angling, so optimal is in quotes.)

If you just replace the card no questions asked, it's unexploitable. If I claim to have seen an ace, but you really had a lousy card, now you get your card replaced which hurts me. If I really did see an ace then your card really should be replaced. If I claim to have seen a lousy card but you really had an ace, well, it sucks I've taken your ace away but I either didn't know that or I did know that because it flashed. Either way isn't an angle.

There is a way I can cheat, and that's to see a lousy card and keep quiet. But that's all the more reason for dealers to aggressively fix their own errors and for players who didn't see the face to still report it.

Sounds like potential collusion

I saw this once while I was playing and talked to the floor away from the game. He came over and watched for a minute and then talked to the dealer after his down. When that dealer came back he was still doing it so I told the same floor again and left it at that. The rest of that day it improved slightly, but I could still basically see every card that the 2 players to my right and 2 players to my left had every hand. I spent those downs either away from the table or watching my tablemates eyes to see if anyone was watching the dealer's hand for an advantage.