It's a close call - I make this based on the fact that GitHub is viewed as an anti-choice by some in the community, a huge change from the "you don't use GitHub?!?!" energy they had pre-acquisition.
The MS acquisition traded the developer community to briefly appeal to enterprises, then quickly let both down.
Both the startups I worked at and the mega corps are all on github or moving there from bitbucket. They are in a bit of autpilot mode in terms of useful new features aside from actions but I can't think of any new bitbucket feature since I graduated and started working.
Bitbucket is not a player, as you said there are only people leaving. Gitlab has a better enterprise posture than GitHub and can be deployed more securely. Most developers aren't unhappy with GitHub, but IT and security teams are.
I dunno, for me Github is better than it was pre-acquisition. Sure, the rate of improvement has slowed a lot, but they did fix some old annoyances. But come to think of it, I can't really think of any ways that it has enshittified. I don't use any of the CI/Actions stuff though.
