Team Fortress 2

Official casual matchmaking can be rough, as you can gather from the comments, but it depends heavily on what maps you select to play and what region you are in. If it turns out to be too rough, check out community servers instead; many will be heavily modded custom stuff, but many more will be just plain vanilla gameplay.

Also, pick up mastercomfig and go through the installation. It will improve performance and also make the game look a bit better if you have a better PC.

If you end up liking the game, I would drop a few bucks to buy some crate keys from the in-game store. This will make your account no longer F2P, greatly expanding your backpack size. You can trade or sell the keys later on the community markets to pick up all the weapons and some hats (check scrap.tf, it's a good site for this).

I promise you that despite the garbage that has accumulated over like 15 years, it's still a good game. You say you've played Overwatch - that game took some inspiration from this one, so you may feel some similarity. Good luck!