Colt is no longer the name in AR-15s
And while that might be
your opinion, it is still the standard in volume produced affordable AR weapons. To do better, you can go to a custom builder like Les Baer or Wilson Combat, but you will spend twice the money or more to get a rifle that really doesn't fill your needs any better than a Colt.
When doing the research on quality of build and components, Colt pretty much has all the components a person looks for in the gas AR-15.
Many are jumping on the piston gun, but all the bugs are still being worked out and the piston driven action may well turn into the AR of the future, but it is still on the way up, and quite honestly may not be worth the price yet.