I still don't see the problem with dipping.
In ADnD, a fighter mage was only 2 levels behind in both classes...
So dipping 2 levels of fighter in exchange for abilities, which will turn the wizard into a halfway competent fighter mage seems reasonable to me. NOT getting a subclass and one/two less feats and being a bit more MAD too.
I really don't get, where all the dippophobia comes from?
Dipping is a feature, not a bug. Getting strong features is necessary. It is just that those features may not be too strong.
Channel divinity as written seems to strong. Old Hexblade always was too strong. But those are specific problems, not general ones.
Some people look at character classes as LEGOS; you can just grab the pieces that make your character concept work. Thus your "Pirate" might be a Barbarian/Fighter/Rogue/Ranger, if that gives you the abilities you feel you should have.
Other people see character classes as the core of a character's identity. Your character is a Fighter. Or a Wizard. Or a Barbarian. Not some Frankenstein cobbled together out of the best parts to create an abomination.
In AD&D, if you were a Fighter/M-U, that's what your character was. You never stopped being that, and it wasn't like you could grab a few levels of something else on top of it.
*With the notable exception of dual-classing, which was required for the 1e Bard build. Despite the name, you could pick up multiple classes with dual-classing, though constantly having to go back to level 1 and having to pretend you didn't have any other class abilities had it's own issues- I don't know of any insane dual-classed characters, but now I wish I had an AD&D game to join to see what's possible!
On top of all of this, there's the issue of balance.
If a Paladin/Sorcerer or a Paladin/Warlock seems to be more potent than a Paladin single-class, the question becomes, why should anyone be just a Paladin?
I personally like multiclassing, and the ability to do it, but for some classes, reaching the highest levels doesn't seem terribly rewarding. Especially when you consider how few games go on to those levels in the first place.
Even if [Class] 20 is more powerful than [Class]8/[Class] 12 in the long run, if [Class] 4/[Class] 4 is stronger NOW than [Class] 8, and the campaign is unlikely to go past level 11-12, what's the better choice?
If the better choice is multiclassing, that presents a problem. And yeah, especially in 2e, multi-classed characters did tend to be better than single-classed characters, because the few levels you lost didn't tend to give you that much once you hit high levels, in exchange for a lot of versatility- but at the same time, the low levels were a real grind.
In 5e, maybe waiting a level for that new spell or extra attack seems painful, but it's a lot less painful than a Half-Elf Ftr/Thf/M-U desperately waiting to earn 3,750 xp to get his 1/3 of a d6 hit points!