Amrûnril
Adventurer
There are definitely some balance issues with a la carte multiclassing. Some abilities are too strong as a one or two level dip (eldritch blast, rage). Some higher level abilities are too painful to forgo (extra attack, high level spellcasting). But the system gives an amazing level of customizability, and I think that getting rid of it instead of refining it would be a huge mistake.
Sometimes a player has in-character reasons to add a class they weren't planning on, or to stop taking levels in a previous class. Any system that requires a fixed choice at early levels of that requires an even division of levels isn't going to work in those cases. And the process itself of combining levels from multiple sources to realize a distinct character concept is fun for a lot of players..
I also think that finding compelling combinations of subclasses is one of the most interesting elements of multiclassing. A Moon Druid multiclass and a Wildfire Druid multiclass are completely different, both mechanically and thematically, and a system that didn't allow that sort of choice would be a huge step backwards.
All that said, I think providing multiclass-like options through feats or subclasses is a great idea, I just think it's important that these be alternatives to the current multiclassing system, rather than replacements.
Sometimes a player has in-character reasons to add a class they weren't planning on, or to stop taking levels in a previous class. Any system that requires a fixed choice at early levels of that requires an even division of levels isn't going to work in those cases. And the process itself of combining levels from multiple sources to realize a distinct character concept is fun for a lot of players..
I also think that finding compelling combinations of subclasses is one of the most interesting elements of multiclassing. A Moon Druid multiclass and a Wildfire Druid multiclass are completely different, both mechanically and thematically, and a system that didn't allow that sort of choice would be a huge step backwards.
All that said, I think providing multiclass-like options through feats or subclasses is a great idea, I just think it's important that these be alternatives to the current multiclassing system, rather than replacements.