I'm currently building a kind of game website that needs a login system. I like the idea of going passwordless and just checking an email and clicking a button

I'm currently building a kind of game website that needs a login system. I like the idea of going passwordless and just checking an email and clicking a button. That seems low friction. I like that you don't require a credit card from me. I also don't expect to charge users ever so I like that the service would be free. On the other hand, my hope in building my current project is that I'll show it some people and they'll enjoy it and I'll keep working on it and more people will keep using it etc. If that does happen I'd want complete control over the login system and I'd hate to be in a situation where I couldn't make changes to the system (or remove your component) because my users were already logging in via loginland. For example, I imagine a future where people love my game it's taking off, but there are problems with your service. If I replace it, I have to figure out a way to preserve the accounts and logins of current users while simultaneously giving a good experience to future users. It seems easier to just do a minimal login system on my own now and improve it as needed. Finally, if I were in a money making venture, I'd have the same concerns plus I'd realize the cost of 5% is probably disproportionate to the savings - which would be having to implement a very well understood solution.