Is setting up my own SMTP server to send email a waste of time with regards to deliverability?

I've been running my own email server for 17 years, including hosting a large mailing list, and although it takes time I find it's perfectly possible, even today.

Most of what should be done, you're already doing; but one factor you don't address is what kind of IP address you're using. Many mail providers outright blacklist (or use as a strong marker for spam) IP address blocks which traditionally act as spam sources. First and foremost, those have been the domestic broadband address blocks, which if directly sending email are almost always part of zombie botnets. But in this case I note that your server has a Hetzner address, and is therefore very likely a VPS:

[me@anni ~]% whois 144.76.81.247
[...]
inetnum:        144.76.0.0 - 144.76.255.255
netname:        HETZNER-RZ-BLK-ERX1

VPSes are disposable, and a perfect target for senders who want to fire up a server to send out a couple of hundred million spams then disappear again. I imagine that at least some big providers have taken to adding VPS blocks to those internal marker/black lists.

My mail server is a physical box, painfully and expensively hosted at a colo facility, and possessed of some IP addresses from a range reserved for real server colo (or, more precisely: a range not known to be used for domestic or VPS purposes). These are much less likely to be regarded as structurally tainted, because it's much more trouble and expense to set up a physical server than a VPS, so a spammer is much less likely to do it.

So I guess my precise answer would be that it's still perfectly possible to run your own SMTP server, but it may require more pain than you have yet undergone. Sorry.

Don't give up hope completely. Running your own mail server is sometimes a pain but it sounds like you're doing everything right.

Generally I would say if they aren't blocking you outright (i.e. you get bounces back) then it's a content issue. Try adjusting the content somewhat. Microsoft aren't the best at anti-spam but they try hard for their users - sometimes too hard. Tell your users to whitelist you - add you to their address book is the usual way to do this.

Also make sure your mailing list software isn't setting your content as Precedence: junk/bulk. That might cause you problems.

Unfortunately none of this stuff is easy. Deliverability is a bitch. Mostly it is trial and error.