I hate to be that guy but how on earth do you have a "high-end" system (your words) that does all this?
Sure, there is some boot up time to warm everything up, but there are no ads and no user agreements etc on mid to high end systems.
Even my entry level system (denon avr, lg c1 oled, appletv4k and ugoos as media players) does not take more then 10 seconds from totally off to showing the menu / plex interface, and no user agreement popups or ads
My system is very similar to yours. I’ve got a UHD player, XBox, Plex Server, and a half-dozen retro gaming systems in the mix. But apparently I'm not as patient as you (and others that responded) are.
I find 10 seconds to be intolerable and unnecessary. I’m old enough to have been spoiled by the analog world where power meant you were ready.
Not only is the time-to-wait painful, occasionally the HDMI handshake fails or the TV powered on quicker than the receiver’s signal was output and its input selection “picks” the wrong input or wrong display settings. So now you have to consider the order you’re powering things up, because the TV is “smart” and if you tell it to choose an input that isn’t ready, it’ll self-select one it thinks is ready.
And if I’m using HDMI-ARC, which I frequently do when using an over-the-air signal, if the TV powers on sooner than the receiver, the TV falls back to its own speakers. So now I’m stuck navigating the TV menu to get the audio through my SVS speakers instead of the ones in the TV.
Occasionally my TV has an “update” and then its apps have updates and then the update presents a new “user agreement” with all the data harvesting options pre-selected. If I don’t use my system frequently, two of the devices in the chain may want to update!
And after all that, if I’m watching physical media I then have to wait for the disc to be read and navigate through forced ads or trailers or piracy warnings. If they aren’t forced, I still have to intervene to skip them and get to the menu. But don’t select anything too fast on the menu! It has its own animations it wants you to watch before it will show you what options you have.
And all of that whining doesn’t even cover the wasteland of options available to remote control and make sense of the Rube-Goldberg AV system. The best option (Logitech Harmony) bailed leaving consumers with nothing but the Chinese schlock that hollowed out the market in the first place.
From what I read your problems are all traced back to CEC.
I'm not using CEC, and I dont have any of the problems you describe here. but that's because I dont let my devices tell each other what to do. I use a harmony remote for that.
Logitech stopped selling new harmony remotes, but all the infra to configure them is still online and managed by them, and as soon as you have configured the hub, it does work totally standalone.
I'll worry about another brand when I buy new hardware and the harmony configuration infra is no longer online (I'm pretty sure there will come an opensource alternative)
About the update: the secret here is 'dont connect your tv to the internet, there is 0 use for that'
Sure, there is some boot up time to warm everything up, but there are no ads and no user agreements etc on mid to high end systems.
Even my entry level system (denon avr, lg c1 oled, appletv4k and ugoos as media players) does not take more then 10 seconds from totally off to showing the menu / plex interface, and no user agreement popups or ads