How exactly is that solving the problem? If anyone does something remotely spammy from that ip, your mails are spam again too. And you probably got lucky that the ip you're sitting on was warm and trusted to begin with. You didn't really find a solution, the problem simply hasn't occurred yet for you or you are not aware of it yet.
GP is right. Self hosting email sending (and by that I mean any solution where you control the mail server) doesn't work unless you accept that you will randomly end up in spam folders and sometimes not delivered at all.
So either get a package at some of those smaller providers with a dedicated IP, or go to one of the big providers (Google, Microsoft) and use their highly trusted IPs, that everybody whitelists by default.
Instead, the hosting provider will operate a mail service for you, much like Microsoft 365, G Suite and the like. They will also take care of the IP reputation, SPF, DKIM and all.
However, I dunno why people only mention the cloud providers, while services like MailChimp, Sendgrid and others offer this for mass emails and companies like fastmail for personal users. The cloud isn't really necessary at all.
Many small busineses have their 'online' presence like that. If I have mail deliverability issues, it's not my problem any more, I can call Hetzner. And before I started using it I was sceptical because if Hetzner did not fix the reputibility of their IPs or the spam from their other customers, it would be a problem for me. But so far, it worked quite well!
I self hosted because I wanted to prefer not to be part of the huge o365/Gmail/iCloud monocultures.
Last year I moved my mail to an old fashioned shared webhosting account at Hetzner. Very happy with it!