They've changed. Now they routinely redesign stuff. Add stuff that no one wants and cripple or remove those they want. And then make it slower.
Outlook web is a perfect example. It's 10x slower since the last redesign and their exclusive killer feature - SWEEP no longer works for me.
Have you sent feedback?
Having lived through Windows phone's saga, Windows 8, 8.1, 10 and the first set of outlook.com redesigns, I know one this - their feedback tool is a placebo button, a self therapy session to get stuff off one's chest.
Microsoft doesn't listen to feedback through their official channels. They might step back temporarily when there's overwhelming negative outcry from the news but they'll definitely attempt it again after a while.
That's not the Microsoft way. It'll accumulate features without ever deprecating bad features, not fundamentally improve. Look at Outlook. That terrible threading has its roots there. There'll be _someone_ out there who loves it, so it'll never go away.