If the game was to keep alignment in some fashion, then you might as well stick with the current 9 alignment system. Going back to 4E's five alignments or OD&D's three alignments is pointless, because the issue with alignment has nothing to do with how many alignments there are, but rather what alignment as a system is doing as a whole.
The issue is that alignments are defaulting creatures of all types to a baseline of how they behave. For some monsters, obviously that isn't as much of a big deal because their entire existence is predicated on said thing-- undead, devils, demons, celestials, aberrations etc.
But any intelligent race native to whatever setting you are using does not and should not have default alignments because any representative of said race can be anything they want. You have evil humans. You have lawful elves. You have good orcs. You have chaotic dwarves. So with no real baseline to any race's alignments, there's no reason to write them down as though they have one.
Yes, I know some people want to treat certain monsters like orcs to basically be mindless automotons to be mowed down willie-nillie with no thought to any sort of morality for killing them as though they were nothing but zombies... but quite frankly we are passed that point. Orcs in D&D are not mindless evil to be killed just because they exist anymore, and the game doesn't want to do anything that might make people think otherwise... and putting 'Chaotic Evil' in front of their statblock certainly does that. Like it or not... putting 'Chaotic Evil' in a statblock makes players think that destroying them is completely fine, no questions asked. But orcs and drow et. al. are not the same as demons anymore, and thus the alignment system should not run counter to it like it does right now.