Shadowedeyes
Adventurer
I have quite a few friends that are fans of different gish concepts, so I can definitely get that diversity of options is a big draw. And I while do think it's possible to balance the magical gish with the nonmagical warrior, it's quite the tightrope.I get that it's difficult to balance, and 5e has plenty of examples of poorly balanced gishes (I'm looking at you, Eldritch Knight, Hexblade, and Ranger), but I really like the concept of the Gish, particularly because the diversity in possible characters with it. "Gish" just means someone that merges magic and martial combat, which includes Paladins, Rangers, at least 3 Bard subclasses, Bladesinger Wizards, Hexblade/Bladepact Warlocks, about 4 Fighter Subclasses (Rune Knight, Eldritch Knight, Psychic Warrior, Arcane Archer, possibly Echo Knight), Armorer/Battle Smith Artificers, and a buttload of other subclasses.
A holy warrior that burns spell slots to explode demons? That's a gish. A finesse skald that slices apart enemies with a magical sword while singing a party-bolstering song? That's a gish. A heavily-armored tinker that thunder-punches enemies to death? That's a gish. A tree-hugging shaman that smacks enemies in the face with a Shillelagh'd quarterstaff and commanding an animal companion? That's a gish. All of these, and many more, qualify as gishes.
However, when compared to nonmagical Barbarians, Fighters, Rogues, and Monks, none of these invalidate any of the other options. They have their own strengths, Gishes just have to have more limited resources than non-magical warriors and be restricted in unique ways (Paladins have to be melee, Bladesingers can't use two-handed weapons, Hunter's Mark and Hex have time limits and require concentration, and so on).
Which I think is part of my problem with it. It's way too easy to end up on either end. You either have a mess of a character who can't really contribute in either magic or martial ability, or you end up with a slightly worse martial character who has enough magic to equal or even exceed the nonmagical character at their own game, often with enough left over to have some useful utility that the nonmagical character just can't match. And this is way more common with martial characters over full magic users, who very rarely get overshadowed by the gish at their thing. Part of this is just the fact that magic tends to trump non-magic in general, but it can made even worse by magic that explicitly is designed to enhance martial combat.
In 5e, I'd say WotC did a pretty good job making sure you won't feel completely useless bringing your Battlemaster Fighter into a party with a Bladesinger, Paladin or other gish character, but I'm not sure that the Battlemaster is bringing anything unique or special to the table either.