Android is widely using mobile operating system It has a high market share in mobile operating systems field. Android is an open source so who can their own custom operating system.
There are two types of Android, one is stock Android and the other is modified Android. Stock Android is a clean Android OS in which there is no bloatware and there is no change in the performance of your OS.
But there will be a lot of bloatwares on the tweaked Android which will slow down your mobile and you can't wait for the Android software update.
This is because the software update will come easily on stock android os but with a bit of delay in the modified Android OS the width may not come otherwise