The character is only a burden if the other players and DM have agreed to overpower their aspects of the game in comparison to yours, and they don't give a rat's ass that you're behind.
Right, because there's no math in the game at all.
It has nothing to do with what other people in the group are doing or how the DM runs the game. The system itself has an internal mechanic that is fundamentally flawed and requires certain choices to be made in order for the balance to be restored.
This is, of course, assuming you use the basic rules for balancing combats by XP and level. If you balance an encounter using the method recommended for doing so, and you play a character without optimal choices, you end up playing a character that doesn't do enough damage, or doesn't hit often enough, or doesn't heal enough, or gets hit too often, or can't heal himself enough, or fails at every skill challenge, or whatever it is that your character is supposed to do due to their role and skill strengths.
As I said, we are not playing "Peasants & Peons". We're supposed to be playing a game where we are the heroes. That means we should be capable of actually succeeding at the challenges presented to us. The success shouldn't be guaranteed but neither should it be next to impossible. By not optimising a character, you're bringing it in under par and that creates a drag on everyone else. By bringing in an optimised character, you're simply adjusting for the flaws in the system and bringing everything back into balance.
There is an extreme beyond optimisation that goes into min/maxing, but that is another issue entirely.
The funny thing here that you don't seem to realise is that I'm on your side. I want a system where I DON'T have to choose these options in order to make a balanced character. I would love nothing more than to have a character be able to speak ten languages through feat choices. My argument is that I can't do that without becoming a burden to the rest of the group by not fulfilling my role successfully in encounters, whether they be combat or non-combat.