I suspect the pushback comes from the contrasting degrees to which the different classes have the mechanical tools to reliably empower those team contributions and affect change in the campgain through their mechanical agency, particularly given as the non-mechanical contributions (e.g., "the friendships made along the way," etc.) are often irreproducible between campaigns, tables, and groups.
I don't think you're getting it. What @Aldarc said has absolutely nothing to do with DPR. It literally has to do with almost everything else in the game, except DPR.
There's at least two camps on this. On one hand you have @Minigiant talking about things like how awesome spells like meteor storm are and how many attacks a fighter should have to balance that out. Then it gets pointed out that DPR isn't everything and suddenly it's not about DPR at all.

Out of combat? If a fighter wants to contribute they can take feats to get bonuses or use ASIs to do things other than just be good at fighting if they want. Observant and prodigy can be taken by any class, but a fighter gets more feats. Even so, a lot of people don't care as long as someone in the party has the appropriate proficiency. But what does a wizard add outside of combat that a fighter can't? Teleportation? Cool. You get from point A to point B more quickly. But would the stories really change that much if teleport wasn't an option or would the DM just tweak the story so it doesn't matter? Would Star Trek really have been much different without teleporters? Or was it just convenient? IMHO it's a nice convenience and shortcut but that's all.
What makes wizards so far above and beyond fighters that doesn't involve DPR and meteor storms? Things like alter self are nice, but a hat of disguise is an uncommon item. Charm person just makes someone a friendly acquaintance and they know they were charmed. Suggestion is powerful but depends on the DM's interpretation of reasonable and I've never seen it used.
People keep doing this bait and switch. It's DPR! No, its out of combat! But I don't remember the last time anyone actually stated what out of combat capabilities they think are so game changing and not just convenient. So what exactly are you talking about?