I feel like you somewhat misunderstand the concept of a time control. The clock is a part of the game. If you are up a piece in a complicated position with five seconds left on the clock that may well be a losing position for you. Sure, the engine may show you +4, but the clock is an important part, especially in blitz.
Importantly, if you spent all your time getting a good position while the opponent played quickly to conserve their time, then they performed better, because they got to a still tricky position while using less thinking time.
If you don't like this flagging mechanic (I for one do not), increment exists for a reason. There is still some time management there, as playing on just the increment means you don't have time to think deeply. However, it allows you to keep playing instead of losing on time. If you play without increment, it is your decision, but then you have to be up to take the consequences.
