Zardnaar
Legend
That's a particularly weak edition war talking point. You could play whatever martial concept you wanted in 4e and have a viable character. You cannot say the same of 5e. Nor any other edition.
It's not true that 5e classes can help cover for eachother in 5e? So, a Cleric wouldn't heal a Monk that got hurt in melee? A Wizard wouldn't cast Magic Weapon so a Fighter could harm a monster resistant to normal weapons? A Druid wouldn't cast Pass Without Trace on a Rogue trying to sneak up on a particularly observant enemy? A Warlock wouldn't cast Silvery Barbs to help the Barbarian pass a saving throw and keep his rage going...?
Is it that these things don't happen, or the game is so easy you don't need to work together...? Beacause, as iffy as CR is, I don't think counting on every fight being that easy is practical, unless the DM is just going to adjust everything on the fly to assure the party's success (or at least survival -which, honestly, not a bad idea).
As far as an all-one-class party being generally effective in 5e, well, all one full caster class or all paladins is likely to be pretty robust, and that's more than half the classes, right, there, so close enough to 'generally,' sure, granted.
OK, I guess you might be right, 5e may have arguably abandoned the age old D&D-ism of the Big 4 and the balanced party.
Mono class parties were talked about at least as far back as 1989. 2E material covered them.
PHB 4E archer fighter not the plug ins they added later? You would suck hard.
You could play a decent archer fighter eer edition from 1E on its one of the most basic concepts as well.