I'd be more understanding if GTA Online hadn't already shipped its first version in October of 2013. Surely there would've been some time after shipping the first version to profile the game.
But I should note that once you ship a product in this space there is a heavy emphasis on not breaking much. Changes are for the next milestone (seasons, service packs, new features). There's very rarely any emphasis on "fixing" something because it could introduce even more bugs and Producers prefer sitting on a stack of known issues than addressing them with more unknown ones. Since known issues have a known cost.
Until it gets so bad that you have to make health patches, we made such patches (and referred to them internally as "Sanity" patches)
Usually different staff rolls on and off at different times of product development and post-release lifecycle. I understand that most programmers would have been rolled off a while before launch. You early on have people build or adjust the engine and tooling, but later on you don't need most of them anymore and things come down to creating content.
Usually in software development you have different people over time, because of individual churn, not because you are changing the role mix
I think that Rockstar deserves some blame here, especially since this problem might well be a consequence of their notoriously bad development practices.
One philosophy I heard in my days of programming (not sure how I remembered this but its still out there) :
Make it work, make it right, make it fast. -- Kent Beck
Rockstar has virtually endless resources and the game has been out for many years. for years, they didn't reduce the extremely long load times? not only embarrassing, but shows deep incompetence and lack of respect for the craft and for end users.