There's all the evidence it's exactly what Roth IRA is for in its very design. If whoever designed it meant it to have caps - they would make it have caps. They know how to do caps - they did caps on contribution, they did caps on income for being allowed to contribute (which btw is super low). They didn't put caps on the account size because they didn't intend to have them, not because everybody who designed it suddenly had a stroke and forgot caps are possible.