Yay. Let me pay for the privilege of sitting in a cramped seat in a cramped aluminum can longer than I have to.
A better seat (even just middle economy [comfort+ in Delta lingo]) or any priority boarding group is enough to get space.
If you don’t have status, your strategy is a great one. Delta is pretty good at not trying to charge you in that circumstance. It also helps the flyer’s case that their A321 mainstay was configured with a cabin that provides insufficient overhead bins.
I'll take the other benefits, too, and they're "worth it" as long as you don't spend a bunch of money to get them. There's a real dollar benefit to free Economy Plus, checked bags and the mileage multiple; but of course how much that's worth to you depends on what's important to you, let alone the intangibles like pre-boarding or better customer service.
So far, the status and miles I've earned haven't involved spending any money I wouldn't have otherwise. With the sometimes exception of spending a little more to stick with United. Which is of course the point of a loyalty program. But I've never spent more on that increment than I've recovered in benefit on that flight (like from free Economy Plus). But who knows? Maybe I'll get so addicted I'll be tempted to make a "mileage run".
Also, all those doubling of miles and other perks allow me to get upgrades for free so when I do have flights I really need to sleep on I can take first class.
I have noticed a lot of domestic first-class seats or post-purchase upgrades have become cheaper during COVID to get the airline some revenue from that seat rather than upgrading you or I.