To be fair on Massive, they reacted much better than most devs to feedback.
Yet at the same time they remain quite aloof and quite resistant to taking ownership of issues with the game/admitting things aren't working even though as above in the same breath they say they've moved onto TD2 because the issues with the first game make it more worth spending the time building something new.
A lot of it is little things as well - common complaint for instance is the inventory management and limited inventory space but then they continue to work features like bonus weekends that compound that issue instead of rolling with the problem i.e. double field cache drops instead of increasing the items in the cache or increasing the chance of a bonus item drop in the cache so people have less things cluttering up actual inventory space and can manage opening the caches at their leisure.
Then there is for instance that if an NPC nudges up against you it will kick you out of open UI menus and people tend to go into safe houses, etc. to spend time in the UI menus managing things, etc. so what do they do... put loads of wandering NPCs in the newer ones like Camp Clinton who'll constantly nudge you out of menus... sure you can think to position yourself in a spot they are less likely to wander into or use another safe house but that is a bit beside the point.
Then there are the things that they've never addressed or changed - loads of people have complained about the constant audio spam when you go to the The Terminal about Last Stand - some just aren't interested in even trying it for others like me it doesn't go away even if you do a round - it can't be that hard to add a simple option to mute those kind of voice overs.
Quite frustrating as I could sort most of the non-balance, non-netcode related issues in probably not more than an afternoon and if their authoring tools are any good it should be possible to build in 100s of hours of extra content without adding a single new line of code or extra game assets just reusing what is there
I'm not sure if it is the developer attitude or Ubi shackling them or a mixture of both but the lack of taking ownership of issues and the lack of an agile mindset to working around the ones that aren't easily solved is putting me a lot of spending any more money their way.
EDIT: I'm relatively late to the game - only been playing for a year - I suspect someone who has lived through 1.6 etc. patches probably has a little different perspective.