You want your average view duration to be as high as possible. I constantly hear people say "at least 50% because if only half of your audience make it to the end, was it worth making the video at all?" but personally I find that mindset incredibly depressing.
THAT is why I instead prefer the mindset of "aim to have your next video's audience retention better than the last"
You always want to be aiming higher, but if you don't get any higher, don't let that depress, just means you want to try a different approach to get your next videos better.
I regularly have 10% audience retention, and that has made me incredibly depressed at times, but instead, I simply try to make my next video aim for 15%,then 20% then 30%... over time try to get your videos as high as possible, and with time and learning and experience, you WILL gradually get your audience retention higher and higher if you learn to analyse your videos watch time graphs and adjust accordingly.
As for CTR, they may say 2%-10% but I'd personally not want to go any lower than 4%. I try to make sure my thumbs stick to around 5% minimum, and if they don't, I try to change my thumbnails a bit. But sometimes a good thumbnail won't save a bad topic, and then no amount of title or thumbnail will boost the click through rate if the topic isn't interesting enough.
My GOOD performing videos get 6% consistently, and I'm hearing lots of rapidly growing channels manage to get 12% at times. so I'd strive for 6-12% personally. That's how I do it. 2% might be "average" but you don't want to be average, that's why you should AIM for something much higher, but also realistic as well. I like aiming for a consistent 5% minimum.