Maybe because improving audience engagement is relative to each person's channel? Or that retention time is not as important as watch time? Heck, the only thing retention time is good for is to know how long your videos should be. And finally, there are plenty of advice given here talking about call-to-action and retaining viewership.
Not everyone does YouTube so that they can grow at high levels or look for financial freedom. There are plenty of people here that do it for a hobby, for enjoyment, and for seeking out their passion. No amount of views or subscribers should stop people from doing that.
Instead of trying to put people down for their own intentions and their motives, how about you spend some time sharing your own experience in being successful?
It's false, nowadays average watch time is more important than subs. Make a simple test : Take 2 videos speaking ablout the same subject. Watch 10 seconds of the first one and the whole second video. You will soon notice that other videos from the second channel will appear in your recommandation tab. It's much more easier to make a video that people watch than a video that makes people sub to your channel.
For the second point, why do you think audience retention is something "relative" ? There are plenty of articles and videos speaking about how to keep your audience's attention.
I know that my message is different from what people are used to one this forum : "never give up your channel is awesome", "keep going and your turn will come" etc.. But is it really helpfull ? From what i have seen on this forum people have forgotten that a good video is a video that people watch. A good channel is a channel made of videos that are watched. Making a 20 minutes video with a 10% average watch time must be seen as a disaster. What will help a small channel : a 5min long video with 80℅ a.w.t or a 20min video with 10% a.w.t ?
Nowadays youtube's algorithm nows better than you what you want to watch, and it will show you some channel wheter you follow themor not. So, instead of making 100 video and making 500 views per video after one or two year, one who wants to succed on Youtube should start by learning how to make a 2min long entertaining video, then a 3min long etc.. I personnaly thing that keeping viewers attention is something that one can learn (for exemple a relevant video about that is "how to keep your audience's attention" on Tedx Talk channel).
So i stand on my position : a video has to be watched entirely, from the first second to the last, and it should be the main subject of this forum instead of all these topics asking "when should i upload my videos ?"
