OB1
Jedi Master
If you want to argue that it's meta-gaming, then so be it. I don't agree, but it's irrelevant to the actual point, which is that failure on your part may lead to suffering for someone else, or possibly the entire group. If you consciously choose to make your character less powerful than they could be, and someone else suffers because of that, then it's your fault.
By presenting a balanced game, without superior and inferior options, it avoids putting any player into that situation. Your choices become about what type of character you want to be, and not about your obligations to support others to the best of your ability.
By balancing for sub-optimal characters 5e has created space to create the character you want without having to worry about your obligations to the party and without the immersion breaking fakeness of forced balance between character options.
And again, by your reasoning, a party should never leave the confines of the local tavern and let someone else deal with the world shattering events, lest you cause the party to suffer death ;-)
As for my Gnomish Tavern Brawling WildSor/Feylock/GlamorBard Drixel Habblepox, he’s currently level 15 and just saved the party from a TPK thanks to a well timed Enlarged Grapple against a vampire.
Of course, 9 times out of 10 it’s the GWM Goliath Bear Totem Barbarian who’s been min/maxed to the hilt dominating combat, but it’s that time Drixel saved the day that everyone remembers.
Also worth noting, the other two PCs in our group are also less than optimal, yet we routinely fight above our level in CR and above deadly encounter xp.
We don’t make suboptimal choices in combat, that would be disruptive and putting PCs at risk, but the contract at our table says build the character the way you want, and the group will work together to overcome as a team.