People don't complain that clerics do less damage because they have other powerful abilities like healing.
A monk should do similar damage to other classes. He doesn't do a great deal else in the course of battle. He pretty much hits things. In a group game have fast you do damage is the only way to balance classes that bring nearly nothing else of substantial value to the table.
Monks do good damage. A free bonus attack plus kind for another additional attack plus extra attack plus scaling weapon damage isn't bad damage at all. What they lack is feat support for their combat abilities but not taking one feat is just taking another for a different advantage.
Monks are good at getting to key targets for attacking by speed and mobility, and using stunning fist attacks. They are also the only class with proficiency in every save and can give themselves advantage on the saves.
Open hand monks have an SoD attack and that tends to trump higher damage anyway.
The poster from the other thread that you seem to be referring to was complaining that his blaster sorc is ineffective at dealing damage, relative to a barbarian. I think it's fair to complain that a class that is forced to be tightly focused at what it can do (small number of known spells), and using a subclass specifically made for blasting, is ineffective at dealing damage.
When does the barbarian can launch AoE damage or twin a control spell? Believing that the sorcerer should do more damage than the barbarian because of the sorcerer's small toolbox is backwards when the barbarian had an even smaller toolbox. ;-)
Why should the Wizard ever dominate? Most of the other classes don't get to remake themselves based on what they need to be good at a particular day, or to decide that today they're going to be nearly as good as the Wizard at the areas the Wizard is 'supposed' to dominate. So why should a class which gets to be a Jack of All Trades also get to be a Master of One and a near-Master of a bunch of others?
Wizards almost never dominate. With less at-will damage than warlocks or weapon users, less burst impact than a sorcerer or fighter or paladin, higher squishy factor, legendary saves, and utility spells that are replaced by skills the wizard shine moments are the rare occasion a ritual or spell is actually available that might be important out of combat, AoE softening salvo's, and most commonly controlling effects and buffs to watch the heavy damage combat classes shine as a support option.
Wizards are often useful but dominating anything is an overstatement.
In general, balance is measured by perception of contribution because the contributions are often apples to oranges. Damage is more quantifiable than many contributions and often the topic for discussion because it's quantifiable. I use it frequently too. I don't think it's the only consideration and I think it's important to stress that other considerations have subjective value because the players don't start with the same priorities or values.
Damage comparison is more relevant with the monk and another similar class like a rogue or ranger but it's still only part of the package. All the arguing aside, I find it mostly an academic exercise.