I’m an oddball who can zone out for hours while running without music or other distraction, but not many people are like that. I focus on my technique and form more than anything when I’m doing my really long, slow, “boring” runs. BUT! I always run someplace interesting. During marathon and Half IM training, I’ve always run some coastal scenic route, and I very much look forward to those runs and seeing the sights. Changing up the route helps keep my on my toes, too. That’s what works for me.
As to your suggestion about the half vs. full - if a full marathon is a “bucket list” item for YOU, do it. Otherwise, don’t do a full marathon to impress others or because your friends are doing it. Half marathons are GREAT races, 10Ks are awesome. Both are probably better for you long term because they exact less physical toll, and you can get into great shape training for those shorter distances. Plus, I find the training less boring because there can be more track work involved, and your long runs aren’t so painfully long!
“We” - endurance athletes - place way, WAY too much emphasis on going longer to further our goals or impress our friends. There is nothing wrong with setting a goal to go faster at a shorter distance. In fact, I’d tell you that I probably have more fun training for and racing shorter distances than slogging through the longer ones. There is no part of me that wants to race an ultramarathon… I’d much rather try to PR another marathon, half, 10K, etc. YMMV.
I’d also add that those shorter events - 5K and 10K runs, sprint tris, Cat 4/5 crit series - indeed need us to participate to keep them viable, and those are the races that get more people involved in our sports, thus making those sports more lucrative for equipment makers and get the die hards like us better gear to play with!