It's a massive question, and I think quite a lot of the argument comes from the fact that it depends what direction you're answering it from.

As a user, do I like being able to just systemctl enable --now whatever.service , and have a nice overview of 'how's my computer' in systemctl status ? Yes, that's a big step up from symlinking run levels and other nonsense, much easier.

As an administrator, do I like having services, mounts and timers all managed in one way? Yes, that is very nice - can do more with less, and have to spend less time hunting for where things are configured. Do I think that the configuration files for these are a fucking mess of 'just keep adding new features in' and the override system is lunacy? Also yes.

As a developer trying to do post-mortem debugging, who just wants all the logs in front of him for some server that's gone wrong somehow, which I often have to request via an insane daisy-chain of emails and 'Salesforce nonsense that our tech support use' from our often fairly non-technical end users, on some server that I've no other access to? No, I do not find having logs spread between /var/log and journalctl (and various CloudFormation logs in a web console) makes my life easier. I would be pleased if that got sorted out.

tl:dr; mostly an improvement, some caveats.