Just to be clear - it's the API that's shutting down, not the app. Not that Google has put in effort for the app either, it hasn't updated since health connect afaik, but health connect is the health and fitness tooling going forward.
Fitbit has health connect support now, so even if they shift and drop Fit (I hope not, though I also hoped they wouldn't kill the web interface), and make Fitbit the main Google fitness app, it will still work with Fitbit as the app.
Not really the question I was answering, but that's not actually a health connect problem.
Withings had an issue, and the way they were connecting to it, which caused a battery drain. To be specific, withings health mate was constantly reading health connect data, which caused a massive power drain.
I'm not aware of any other battery issues with health connect other than Withings and their Health Mate app (specifically reading, not writing).
(Edit: why, why would autocorrect change writing to riding? For shame. To me, for not noticing sooner.)