Legendary Actions and More of Talakeal's Gaming Horror Stories

[zinycor]

Is there a point at which specialization detracts from party success?

Sure: consider a hypothetical character. He can deal infinity+1 damage to anything, as long as they're exactly 20 feet away over open terrain, are wearing a blue shirt and white pants, and have no more than 6 fingers but fewer than 10. On the 2nd Tuesday of Neverember, in years that end in 0. As long as it's not raining or cold and the moon must be at one particular point in the sky. If any of these conditions are not met, he can only do the things a Commoner 1 can do. He has 1 HP and 1 AC, and fails all saves.

This is an absurd situation, to be sure, but it proves the point. Crippling overspecialization is a thing. That character would not promote teamwork, because either he kills it in one shot or he's a burden on the party.

In more realistic scenarios, I've seen characters who put all their eggs in one basket. One who was a great controller, but had effectively zero damage output. Against anything that was immune to his control, he was a waste of space. One who could deal tons of melee damage against a single target...once a day, but sucked at anything else. One whose player insisted on not using 90% of his kit, preferring to try crazy stunts instead.

On the other hand, I've seen a lot less of the "jack of all trades" failure states. Mainly because I play 5e, where you don't need to be the best to contribute meaningfully.

IMO, teamwork is enhanced when
DMs create challenges that require multiple people to solve. Preferably N = number of players in the group. And not just bodies, but different approaches. The strong guy AND the fast guy. The magic guy and the buff dude. The talker and the sneak. Etc.
Players lean into the team. Instead of worrying about how to maximize their own strengths and "do everything", they actively try to work well together. This means tactics, it means knowing what the others can do and being able to rely on them to do their part. It means cross-qualification[1].
Systems don't require massive specialization[2] to contribute. This means lowering the escalation of numbers in some ways and making more than one approach have a chance of success.

[1] There's a reason that special forces teams (which are the best analog I've found for an adventuring party) are all cross-trained in a bunch of things. If the medic goes down, someone else can pick up the slack. They can all contribute to everything, even if each has their own specialty. Instead of being a 10/10 in one area and a 2/10 in others, they're an 8/10 in one area and a 6/10 in the others.
[2] I've been told that some editions of Shadowrun were particularly bad about this siloing process. If you weren't a Decker, you couldn't contribute in cyberspace. If you weren't a Mage, you couldn't contribute against magical threats. And if you weren't a specialized Samurai, you'd get blown out of the proverbial water by someone who was. So everyone stayed in their own lane and spent 1/N of the time actively participating and the rest just sitting around. At best.

Underline mine

The hypothetical is enough to show that there must be such a point. That's not opinion, that's fact. And your standards for "objective truth" seem a little...skewed. Especially since everyone is the judge of their own convictions--you can't force someone else to accept evidence you provide. So there's no conceivable evidence that can do the job.

Oh, you can have whatever convictions you want, that's perfectly ok, if you claim those to be objective truths then you need to prove it.