GotaTun is specific to Mullvad and the features they usually add make sense for a public VPN provider. Unlikely projects such as Tailscale adopt it.

Besides, engineers at Tailscale, I don't think, strike me as startled by any hurdle too tall to debug, improve Go-based libraries. In fact, they pushed wireguard-go past 10gbps on Linux-based platforms back in April 2023! https://tailscale.com/blog/more-throughput