I always quite liked the 3.x approach to Multiclassing, while it had issues (favored class, caster level, saving throws, etc), it was an elegant idea, at bottom. Simply treat the next level in each class as an equally-weighted, 'modular' choice when you level up.
4e feat-based MCing was kinda meh - 4e feats, in general were mostly a lot of chaff and fiddly customization options, crowded out by a growing list of feat taxes and broken post-Essentials feats - and Hybrids were, well, not as bad as Gestalts, I guess, but basically trying to do old-school MCing.
5e /tried/ to improve on 3e MCing, to mitigate issues with dipping, for instance, and it does handle MC'd casters better, for instance, and proficiency helps things work smoothly, but, it introduces similar problems in places where they didn't exist before, like extra attack and ASIs. It /seems/ like it should be a simple intuitive system, to just take levels in a class, then start taking levels in a different one - but the class designs never seem to be up to the challenge.
Archetypes don't strike me as quite as elegant or intuitive as 3e 'modular' multiclassing, but, with 3.5, PF & 5e all having tried to improve on the 3.0 system, and none really quite succeeding, I suppose the Archetype approach may ultimately prove more workable. It'll be interesting to see how it turns out.