In my experience, and I used ZeroTier extensively before moving to Tailscale, it fails in a few points:
* Performance was never quite great, especially when NAT was involved. This may have improved, but I haven't used it in a while.
* NAT was hit-and-miss. It would usually work, but would not work frequently enough that I couldn't just count on it.
* Not really easy for some use-cases. Main one for me, having a router both for acessing my LAN from outside, and as a gateway to my home Internet (akin to a VPN service like e.g. Mullvad or PIA). It's possible, and I did use it that way but it required some iptables-fu and it would fail some times - when it did, I would lose all my ability to connect back. This is especially bad if I'm traveling, since I don't have physical access to the router to fix the config. This never happened with Tailscale.
Zerotier really doesn't fail any points, it's just no longer the "hot new thing" or an up and comming startup.
I moved from Zerotier to Tailscale mainly for the fit and finish and Wireguard. Zerotier accomplished everything I wanted for my home network but was never "pretty." Tailscale is "pretty" and easy to use. MagicDNS makes accessing my devices easy as I don't have to set up my own DNS entries.
I moved our entire company off of OpenVPN and AWS VPN to Tailscale. It may not be as cheap anymore, but their networking ACLs and integration with Google/Microsoft for login have made it SO EASY to onboard new people and hardware.
* Performance was never quite great, especially when NAT was involved. This may have improved, but I haven't used it in a while.
* NAT was hit-and-miss. It would usually work, but would not work frequently enough that I couldn't just count on it.
* Not really easy for some use-cases. Main one for me, having a router both for acessing my LAN from outside, and as a gateway to my home Internet (akin to a VPN service like e.g. Mullvad or PIA). It's possible, and I did use it that way but it required some iptables-fu and it would fail some times - when it did, I would lose all my ability to connect back. This is especially bad if I'm traveling, since I don't have physical access to the router to fix the config. This never happened with Tailscale.