This is the Forge Fallacy: A game should zero in on a single purpose, be good at one thing, and forget everything else. In fact, an RPG needs to be good at many things.
5E isn't as good at combat as 4E. But it's better than the other editions, and it beats 4E in verisimilitude and integration of mechanics with fiction.
5E isn't as easy to learn as Basic. But it's easier than the other editions, and it beats Basic in character options and balance.
5E offers less scope for charop than 3E. I missed the part where that was a point in 3E's favor.
And so on. I don't think 5E is the best possible edition of D&D; there's still plenty of room for improvement. But, considering all the elements instead of just one, I think it is the best edition so far.