but where did this idea that if you play too much it's not okay to be bored with a game come from?
Gamer communities fighting on forums is my guess.
I wouldn't worry about it though. When working on games that have fiscal incentive to keep players as part of a community so that they'll be more likely to purchase DLC and/or microtransactions like an MMO or Destiny, the issue of players becoming bored with a lack of content is one that is taken seriously.
Having said that, WoW's expansions that take normal players about one month to complete on their main character and then 3-4 months to complete the endgame content (or at least one more month if they dislike Mythic dungeons and/or raiding) have some players who get through the 3-4 months of content that an average user consumes within a week. It isn't possible to design for that less than 1% of speed-obsessed power-gamers, so no one tries.
However, your example is Destiny 2 and I'm waiting for the GotY addition because their last game's DLC was a disappointment (not that it was bad, but it didn't feel worth the expense or the wait IMO), so you may not be in that tiny minority of content-destroying power-gamers; however, my advice to you whether or not you are in that group or not is the same:
Make an effort to play different games.
Don't think of any opinions on social media or forums as being wide-spread. Even if you get numerous people saying the same things, that is a tiny group of people in a very specific internet place aimed at a game's fandom. We don't trust our game's forums at all to be honest - because the feedback we get from actual play-tests is so different than what we get from fans. An intern still clips bits of it for us that are interesting and well-written with links to the posts, but 90% of it is good feedback with which we agree and already have plans of action in place, 9% of it is cuckoo-bananas even after the intern's filter - but interesting reading, and 1% is helpful feedback that we haven't already thought about, so it's worth slogging through for developers, but I would absolutely tell gamers to avoid it.