The first year of JP was expeditions and backtracking, that had remained the same when it was brought to global years later, and those changes that were made to make them bearable like movement PAs, those were added. Remember the days of having to dodge for that extra speed to clear forest for the 100th time? Not all was sunshine and rainbows in JP, and while I understand the grievances over certain things like localization and some of the funky translations, ie. Healing Weapon Bonus I/II, there's been a lot of the changes that made the game bearable there, that were brought over here.
The RMT issue was a huge problem, especially for the first year of JP, as well as the "lack of elitism/toxicity", sorry, that also existed there. I have been kicked and ignored whenever I had joined lobbies that were predominantly Japanese and left to pick up the scraps during the first year of the game being available. Those players will exist in any game and community as long as there are others that think the same way. It's inevitable really, and that hasn't changed with how much more connected people are.
Population decline happens in every game, Japan had the game go into decline with the end of episode 6 being the last of the story for PSO2, whilst here, I have people I know that would rather wait for NGS instead of playing a game that looks and feels dated, even for 2012. PS2 games had finger movements at that point. and that was nearly a generation before PSO2.
The collabs had content that added a layer to the game, but in the overarching game and scenario? It's nice to have, but even without it wouldn't be a huge issue. That said, it would be nice to have that content, but who knows how much Sega has been hemorrhaging this past year with them having to sell off their pachinko locations? That and licensing outside of Japan just so they can get the license to work with most of the world and their respective laws about such for each country the game is available in.
I'm surprised we even got a SE collab with Nier: Automata, even if it was nothing more than cosmetics to dress our characters in more fancy attire that breaks up the usual scifi/sleek look. It would be nice to get more of that, it's not likely with how the past year was for Sega and whatever obstacles they would need to traverse to get those licenses to even distribute them on a global scale. Remember, this is no longer about Japan now, the rest of the world will have different laws for each country and region.
As for veteran players manipulating the game and market? That's not a whole lot that can change without some direct intervention from staff to slow the increase in cosmetics sold by players. JP had the same issue, but it's more noticeable now with how limited the scratch has been in terms of availability.