Typically, a registrar is not irreplaceable. They could terminate your account so you'd have to transfer to another registrar, but unless their TOS says they ca

Typically, a registrar is not irreplaceable. They could terminate your account so you'd have to transfer to another registrar, but unless their TOS says they can seize your domain they shouldn't be able to completely block you. Even then you have the ability to sue then if they break the contract terms. This is in contrast to the app store gatekeepers, where there are effectively two, each serving a non-overlapping chuck of market, and you can't shop around for better terms or an alternative. Not an ideal situation if something happens with your registrar, of course, but at least there is some possible recourse. The risk of this leading to your business closing is significantly lower.