Hey MukumiTM
Sorry I've been away for a couple of weeks and just coming back to this now. (And about 1,000 spam messages in my Hotmail inbox)
So, I am going to use the helpful info you provided re: dkim, spf and dmarc, to reach out to MSFT via Twitter (because I've read companies actually pay attention to their social media incomings).
Separately I also have Microsoft 365 and started a chat with those guys today, also using the helpful info you provided about the items in the header that should point to a message being spam but yet still bypass MSFT's spam filters. I've had decent luck with that channel - yes, I agree, it's not ideal for power users because they are slow to recognize the problem and ask a lot of silly questions - but in a couple of cases I was persistent enough to get them to acknowledge there was a problem on their side to be fixed in an upcoming release. They said both times that other people had reported the same issue, which I think is the real reason they agreed the problem was on their side. I'll just mention in those cases I think it also helped that I pointed them to MSFT's own support articles being out-of-date (and irrelevant by definition), maybe there's an angle there.
Re: HUB - I don't use Windows or have access to a Windows computer, and the HUB link you provided doesn't open on my Mac. Do you know if there is a way for Mac users to upvote the ticket you submitted? If I can get access to that I'll upvote yours, and create a new ticket myself - because I agree, if enough people start bugging them - and don't let up - they are more likely to make a change than if they aren't being bugged to do anything.
If anyone from Microsoft is still reading this thread, what is your response to MukumiTM's points about the header elements that should call a message out as spam, but your back end doesn't mark as spam? Is there some other reason you won't mark messages with those elements as spam? Because - at least to me - it looks like a pretty straightforward & relatively simple fix for you guys to make. I get you don't care about Hotmail anymore as a legacy product - but at least 2 of us use Hotmail AND are paying customers - shouldn't that count for something?