For sure; and it will continue to be an issue as long as we allow old browsers to exist. I’m definitely not saying you shouldn’t have backend validation, just highlighting where the frontend validation provided by the browser is not as universal as it might appear on the surface.

FWIW I find the native date picker to also still be quite poorly performing in practice, despite quite robust browser support. I wish it worked better but for many reasons, I still see plenty of users (or bots?) who submit dates in the wrong format for whatever reason. My current hypothesis is largely focused on password managers though since they will often do whatever they want directly in the value attribute of an input element.

This is specifically about good UX not about security, validation, or sanitisation.