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for me miui sucks espescialy for lot of bloatware and also the ui is very heavy that crimpled the high specs for low prices that it gives . they update it frequently for adding another bloatware mostly and without any android os update most of the time

for me i already switched to aosp based custom rom because of the heavyness and bloated miui is

Not actually aware of any bloatware. The UI is pretty much simple and highly customisable. I don't know how simple UI falls under your requirement. They don't update OS but system updates to improve performance with the specs. Running for 1 year and more, my guess is it'll last long. That's what I require.
About custom ROMs, I won't rather go in the risks of breaking system bootloader, rooting the OS and flashing a custom ROM for a more good look which in the end run into incompatibilities with other hardware of the phone. Those stuff from A may look good but I've had problems with custom ROMs before and will rather not prefer them.