I don't disagree with your points but your aptTAB example isn't quite right as apt has a number of tools with that prefix (apt-get, apt-cache, apt-key, etc). Plus there's aptitude too.
In fact I often set aliases for apt-get and apt-cache because of apt breaking the 4 key press / tab rule you raised.
or you can use just the "apt" command to search/install/upgrade/remove packages nowadays
whats the point in having a gui installed on a machine that by definition has no keyboard mouse or moniter (Aka a server)
they arent 3 "package managers". yum is a package manager, rpm is a package installer and dnf is a proposed replacement for yum. fyi https://en.m.wikipedia.org/wiki/Unix_philosophy
nearly all linux commands can be completed with around 4 key presses. e.g. aptTAB should give you apt-get