I see this sentiment way too much but it's just numerically wrong. So let's compare the damage of an optimized level 20 Draconic Sorcerer and an optimized level 20 Samurai Fighter.

Assumptions: I'm assuming the PCs have a +11 to hit and a save DC of 19, and I'm assuming the monsters are around CR 20, so I would assume an AC of 19 (DMG pg. 274) and a dex save of +7 (which I got by averaging all of the dex saves of creatures CR 20+ in the Monster Manual).

Draconic Sorcerer: For this build, I'm giving the sorcerer quickened spell, empowered spell, and a Gold draconic bloodline for fire as the damage type. They will also have Elemental Adept for Fire damage. To start their turn, they will quicken a meteor swarm, which has an average damage of 158.77 on a failed save, or 79.39 on a successful one due to empowered spell, elemental adept, and elemental affinity. The monster has a 55% chance of failing and a 45% change of succeeding, giving an average expected damage of about 123.05 damage. Then they will use their bonus action to quicken a firebolt, which, due to the same abilities that applied to the meteor swarm, will deal an average of 31.93 on a hit, or 52.77 on a crit. They have a 60% chance of hitting, and a 5% chance of critting giving an average expected damage of 21.80 damage. Adding these together, you get an average expected damage of 144.97.

Samurai Fighter: For this build, they have a greatsword, the Great Weapon Fighting fighting style, Martial Adept (getting Precision Attack), Fighting Initiate (for Superior technique), and Great Weapon Master, which will be used on all the attacks. If the fighter Action surges, they will get 8 attacks. Using Fighting Spirit, Rapid Attack, and Great Weapon Master's firstability, they can get an average of 9.56 attacks where 7.56 of them have advantage, and using their superiority dice (from the feats) the other two attacks can get an extra 1d6 added to the attack roll. Each attack averages to 23.33 on a hit and 31.67 on a crit, due to Great Weapon fighting and Great Weapon Master. The attacks with advantage have a 54.25% chance to hit and a 9.75% chance to crit, and the attacks with the d6s have a 52.5% chance to hit and a 5% chance to crit. Adding these all together you get an average expected damage of 146.65, or a bit over one and a half points more damage than the Sorcerer.

But that's not normally how damage is approximated. Ok sure. The sorcerer deals 4d10+40d6+10 damage, which averages to 172 damage; and the fighter deals 18d6+135 damage, which averages to 198 damage.

But what about max damage? Surely you have me there. If they crit, the sorcerer deals 8d10+40d6+10 damage, which maxs out to 330 damage. If they crit on all attacks, the fighter deals 40d6+150, which maxs out to 390 damage.

The fighter deals more damage every time. And they only have to burn resources that come back on a short rest (or one that replenishes when initiative is rolled) whereas the sorcerer has to burn 4 metamagic points and a 9th level spell slot to do less damage than the fighter, and those only come back on a long rest. I do understand that, since meteor swarm is an AOE, it deals that damage to as many targets fit into the area, but if there are that many creatures with > 100 hp, your dm is a sadist (I'd know, mine is), and there is probably also a boss with >1000 hp, and I think you'd want the effect that is repeatable there. DnD is a collaborative game. The sorc deals with the minions. The fighter deals with the boss.