I'm with OP - I trained this year for a marathon but when the long run got up over 18 miles I realized "this is not for me". I don't mind a good half, and 16 mile long runs are done, including throwing on the shoes etc. in under 2 hours, but looking at the training plan with 3 months of 20+ mile long runs on there I could just not imagine throwing that many Sundays in the trash. At those distances, particularly in the summer, you need to plan some sort of provision for water or whatever, it's a huge ask to bin multiple hours of a precious weekend day so you can be exhausted the rest of the day, so you can have the privilege of doing a 2:40 long run, probably alone, on race day. But hey, at least the race cost $270 to register for an you needed to travel and get a hotel somewhere (if not a flight!!!) I'll stick to the half marathon as my longest race, they have way less training overhead, you'll be able to find ones near you that are worth running, you'll be able to walk up and down the stairs the next day etc.
All the more power to those who have the time and patience to run marathons, I did run one way back in my high school days so I can say I did it, but there is no real long term attraction to them for intermediate skill runners (who make up most of the board). Sure, if you're targeting an OTQ it's the best event by far, and if you're a novice just trying to push your limits it's a special experience (at least the first time), and if you're a rich person just trying to have a good reason to travel to major cities and impress your Patagonia vest wearing finance bros, hey it might be the thing for you, but if you're just a normal Joe who enjoys the competition, works a normal job, and has some sort of social life, there is zero reason to go for the marathon. Keep it to 5k-Half distance folks.