You don't seem to have missed much. I wasn't a real fan of the first one (just Diablo with guns, no story, no real role-playing aspects... just another brownshooter.) I played it because my friends (irl splitscreen, gotta give credit to a game still willing to do that though) loved the game, and multiplayer with friends is fun even with a sub-par or (in Borderlands case) bad game. Those friends bought BL 2 and I joined them again. We all wished we were playing BL 1 again. The grind got grinder. The drops were even more pointless. And the samey brownshooty backdrops just have some snow poured on them. There was room for real significant improvements... and about the best they could do is give the car a handbrake...
Ok, I liked the handbrake.
The pretentions to "RPG" elements is what bugs me the most. There's zero roleplaying involved in it's miniscule amount of story. It's rolled out via skippable audiologs (very few of them) and a couple of cutscenes, all very easy to miss and totally unnecessary to the central mechanic of faceshooting the same 6 character models a billion times. There's some halfway decent story points attached to a couple of very colorful NPC's thrown your way (Tina's origin story audiologs were actually chilling and the 1 minute of audio was more interesting than any point of the "main story.") But the NPC's only real use is as questgivers, and could (and sometimes are) just replaced with a bounty board. But the biggest letdown in it's "rpg elements" is character building. All of the "choices" given to you in selecting abilities and perks boils down to one thing. Each pre-built character has (at most) 2 effective builds. If you progress along those builds you will breeze through the game barely breaking a sweat (especially in multiplayer.) If you deviate from the predetermined "good builds" and don't get some miracle drop to offset it, you will be repeatedly killed by the starting rabbit-gorillas.
Not that death means anything, just a juant back to the nearest savepoint and an almost unnoticeable hit to the wallet. No point in not just killing your enemies by jamming their battlefield with your corpses. But don't worry, the exploit "good" character builds are very obvious so don't take much trial and error to figure out, reducing the "character building" aspect down to a simple checklist. And combat ability is the only variable in the weak "rpg" elements. Not that it matters, each character has 4 audiologs that explain their backstory. And that's all they get for any story, there's no development or payoff... they are just there to watch stuff happen and playout the grindy faceshooting.
We prefered BL 1, it's use of the Unreal engine seemed to work better for a more precise FPS. BL 2's version was less precise and more "spray towards moving object until the mans falls down." I can see why some people like it. It's "rpg elements" would seem like a world of possibilities to a MMS player. And the grind at least gives you quests and stuff to DO, unlike the multiplayer of the average MMS. The Diablo looter types don't mind grinding for hours for that gun with a .01 improvement to fire rate. And it's easy enough that it's a blast to play drunk. So it has it's good points. But we all hit the (original) level cap a quarter of the way into the 2nd playthru, and didn't see any need to continue playing. We got some of the DLC, and even a cap increase but it was just more of the same. Eventually even my friends who loved the first one... just lost interest. But again, gotta give credit to a FPS that bothers with splitscreen local multiplayer. I can say it's one of the best local splitscreen multiplayer shooters of recent memory... because are there any others? But we logged 100 times more time playing N64 Perfect Dark back in the day, while BL 2 gathers dust after a month or so.