I've seen people in the past make the mistake of correlating "Enjoyment" with "Higher Engagement", but you want to be really careful there.

For example - Flame wars increase engagement, even if people feel drained and frustrated afterward.

I understand why it's a useful metric - It's particularly valuable if your business model depends on time-on-site to sell ads.

But I wouldn't recommend them as a proxy for enjoyment by any means.