Selfhosted

Tailscale is great. The principle concern to me is that your super easy mesh network depends on Tailscale so if they want it they have control, and if they change their pricing or options you depend on them, and though they can't see the data you send they can see the topology of your network and where all your computers/devices are.

I use Nebula, which is more work to set up and doesn't have some of the features, not But if you slap the 'lighthouse' (administrating node) on a cheap VPS it works great. And it has some advantages. But Nebula also troubles me: though it's fully open source and fully in your control, the documentation isn't great. Instead, you can now get "managed nebula", which puts you in the same problem as Tailscale: the company sees and controls your network topology. I fear the company (Defined Networking) is trying to push things that way. Even their android app you can't fully configure unless you use their 'managed' service.

For now, Nebula is great, and my preferred mesh network (I looked into all the main ones). And for Tailscale you can run the administration server yourself with Headscale and be fully in your control.

Actually I wish Tailscale the best as a profitable business. They've created a fantastic service and system. But for me, I'd rather my network be in my own hands and for my own eyes. And, as is OP's main point, once they have enough dependent users, the service might turn much worse.