> Presumably if they get invited to Europe it will be with assurance from the state that nothing happens to them.

I believe ICC members are obligated to enforce its warrants, which is why Putin couldn't attend BRICS in South Africa last year. And this applies to almost all the western world: https://en.m.wikipedia.org/wiki/International_Criminal_Court

So no, it's not toothless.

Putin went to Mongolia, which is a signatory to the Rome statute establishing the ICC, without being arrested.

President Orbán of Hungary also extended an open invitation to Netanyahu despite the ICC arrest warrant, but he isnt' exactly known for being a stickler for the rule of law.