Steam does have a very slow boot time, but the expected behavior is that Steam is always running in the background so I can't imagine it's a priority. I can't fathom a ~3 second wait when installing and launching a game being a real problem. Minor annoyance sure but that's less time than you'll be forced to see stupid splash screens for!
I just quit Steam (so it was fresh in cache, never mind relying on SSD etc.), and started a Steam game. It took 20 seconds before the game launched (not playable, just started).
That's massive. Pretty much any of my non-steam games will be launched and playable within 10 seconds.
(I also hate unskippable intro videos; I'm fairly sure I've collectively spent much longer searching for ways to delete / skip such videos than I have ever lost watching them.)
With Steam already running the moment I double-click an installed game from my list it's taking about 2-3 seconds before they pop open full screen. If you're taking 20 seconds then it may or may not be Steam's fault, but it certainly isn't an intrinsic property of the software.
Sure, but my point is that I tried it without Steam running (most of the time seems spent on logging in to my account). I don't run Steam by default - it'll be updating, downloading patches, popping up notifications and all sorts interfering with my daily life.
That is neither the expected nor the standard use case. If you use a product in a way it's not designed to be used you shouldn't be surprised when it's behaves in a non-ideal fashion. Notifications and auto-update can be disabled.
That's completely unacceptable - the idea that I need to keep a background app running at all times just so I can play a game once or twice a month. Imagine if all apps took such an arrogant approach; our machines would barely run under the weight of the cruft. I similarly avoid Intel installers when using their drivers because they also like to install and keep running a half dozen services and widgets. Same thing with iTunes - I use a shell script to start it up so it can start up all the extra services and kill them later after iTunes exits.
There's a lot of entitled software out there that arrogantly assumes sovereignty over your machine. I don't accept it.