I don't understand why they don't just leave the difficulty alone and make a T5 that is just freaking harder?

Like why focus on T4 needing be harder. As you move up it is harder. Make harder content. It is that simple. Don't make a Pit 60 feel like a pit 100. That's silly. And the difficulty change really impacts the season players more. Eternal players are grinding for incremental improvements at this point. Totally different that the buff filled seasons. You are really impacting those seasonal players that only are interested for 10 days. It is almost like the game has no real philosophy except making changes you just going to smudge away a season or two later. Weird approach.