I think many people have raised the same complaint over the years.
However, arenas are wildly more popular than the alternatives like swiss system or round robin. I think most people do not have an issue with it.
It seems that if you want to have a firm time end to an Arena, there is no choice.
I think it is extremely unfair that chess.com or any arena tournament for that matter of fact, just aborts a game if the duration of the arena has lapsed, meaning good positions for which players worked extremely hard for, all went to waste. Players who are losing abuse this feature by stalling the game, to auto-abort the game later on. Many players are forced to make draws when it is not ideal to do so. Consider the final game and Close pairings earlier, when there is 5 min left for the end of arena is what I would say. What do you think?