Big random factor in the loot so you can go long stretches without any interesting upgrades if you’re unlucky.
There’s a lot of time wasting - go here, now go back there, now go to this place
Leveling is weird and is a big factor in damage. If you’re too low level you can’t do anything except die. If you’re too high level you can’t lose. Sometimes you do too many side quests or not enough
The games typically start slow. You go a long while before you unlock your cool powers, or even the ability to equip four guns.
The writing is meh except for Handsome Jack. He’s a great villain.
There was a mega bundle of all the games before 3 for like $5. Look for that kind of sale.