For example, I currently have installed the 2018.2.16 and one day the 2018.2.17 would be released.
As of right now I would need to uninstall the 2.16, wait for it to be removed, then launch the 2.17 setup. This means that, if by any chance I get away from my pc before the 2.16 is removed, I still have to install the 2.17 and I waste a lot more time than needed.
You could also install the 2.17 first, then remove the 2.16, but this is not really viable: not only one could not have enough space on the hard drive, but the setup process uses as many resources as it can, so you could not be able to install the engine and run another version at the same time.
So you end up wasting the same amount of time, maybe even more, and most of all, no matter how you do it, it takes at least two disjointed steps to perform an action that really should only require one.
Since 2.16 and 2.17 are just patches to the 2018.2 major release, one should be able to simply press a button and update the 2018.2 to the latest version. Maybe you could make this optional, leaving the choice to the user to remove the current version or keep them both, but please add the update button.
I mean, it always worked like this with the old installer, now you're dropping it and it's understandable, but don't leave us with the only option to waste our time.
It all boils down to the fact that when a new update is released it hurts, I get bored and waste a lot of time, while I should feel curious and excited, even relieved, instead. Please fix it.