Prove it. With something else other than flimsy anecdotal evidence.
Great Weapon Master only adds a potential +20 to a Paladin's typical turn. Maybe +30 with a bonus action attack.
That same feat, OTOH, adds at least +40 (+50 with bonus action) to a Fighter's potential damage on Action Surge rounds Lv. 5-10. And +60 (+70 with bonus action) at 11+. Now I tend to agree GWM is overpowered, but the Paladin isn't the poster boy for that. The Fighter is.
Yeah, I'm finding it very hard to feel sorry for the 5e Wizard. They still have legit win-button spells through their careers. Sleep at 1st level, Web at 2nd level, Hypnotic Pattern and Fear at 3rd level (and good old Fireball vs. hordes), Wall of Force at 5th level, Forcecage at 7th level, Wish -> Simulacrum at 9th level ... yeah, nope, no tears for the Wizard here.
3e Wizard was a legit God-tier class, alongside the Cleric and Druid (CoDzilla). It did need to be taken down. It literally made every other class in the game (again aside from CoDzilla) useless in comparison. The 5e Wizard obviously doesn't do that, but even with being a shadow of its 3e self is still among this edition's strongest classes.
I'd say stronger than the Paladin still, in fact, just no longer outrageously so. In fact, I'd say the Wizard, Druid and Bard for sure are stronger classes than the Paladin in 5e. The Paladin is probably in the tier right under. A solid, strong class, but not utterly dominant, has distinct weaknesses and doesn't obsolete anyone else.
Which is why I find it mind-boggling that people want to single out the Paladin as OP. Is it because you all were used to how utterly useless and inept the class was in 3e and 4e?