I often see this repeated, but in my experience self-hosted email works just fine as long as your IP has a good reputation, and isn't on some crappy bulk VPS.
I have a mail server on Hetzner and one on Vultr, neither have problems delivering to any service. That said, both domains are fully and correctly configured. Banners match rDNS, DMARC aligns, I’ve even configured MTA-STS. The IPs aren’t particularly warm either.