If they remove a feature (even if I am not using it) while keeping the price the same - why should I stay a customer? I have a contract. And at least in Germany one party to a contract can not just alter the terms of the contract.

They need to cancel the existing contract and offer a new one. And I would not need to accept the new one. Yes, I would not be using Kagi anymore. But why should I have a business relationship with a company that does not honor the contractual obligations it entered into?