You guys are scaring me regarding the long term (~20 yrs) serviceability.
Bought a new 2018 Crewmax just 2 weeks ago, to replace an "old school" 1994 GMT400 4wd SUV (Tahoe/Suburban/Silverado platform) that was wearing out. Never, ever had those kinds of problems.
But, I live in snow/ice/salt free climate ... hopefully that prevents these seizing/snapping bolt problems.
If this is your first Toyota after a lifetime of GM products, I can understand your anxiety having started with GM myself. In the late 70's, GM design, quality, and reliability took huge declines. When I needed a 4WD truck in the mid-eighties, I shunned the crap GM was offering and bought a one-year-old 4Runner.
I found the design of the truck rugged and simple where it needed to be (drivetrain, suspension, chassis, interior amenities) and leading edge tech where it needed to be (electronic ignition and direct fuel injection while GM was still screwing around with TBI).
That truck was my primary transportation for 32 years and 178K miles. It never left me on the side of the road, but I did replace some minor components (master cylinders, slave cylinders, alternators) mostly due to my own neglect. At about 150K one rear axle bearing went bad and I replaced it.
Through ignorance, I also discovered the mechanical weakness of the 22RE engine...the timing chain. This is not unlike the pan bolts on the Tundra transmissions that surprised the OP; all brands will have weaknesses that have to be discovered and addressed. Except for that one time with the timing belt, the 4Runner had never seen the inside of a Toyota service department.
Once GM began making some progress back with Bob Lutz at the helm, I shopped and bought another GM product...a Malibu LTZ. My understanding is that Bob Lutz personally reviewed the car from concept to assembly line, and it's been pretty good one. Aside from the front strut replacement and a timing cover oil leak repaired under warranty, it's been a pretty good vehicle mechanically (10 years, 85K miles). The interior features and amenities have been less reliable: plastic trim falling off early, one rear door lock broken, driver side door has to be unlocked with the key when it gets hot, little stuff that drives you crazy. Both rear struts have rattles, but still perform as intended, so we're driving it until they don't.
You can quit wringing your hands and worrying about your Tundra not having "long term" serviceability, reliability, and longevity...in those areas, it will in all likelyhood, beat the everlivin' hell out of any GM truck product they're offering now, even if the Tundra does have a quirk or two. Unfortunately, it will take decades for you to realize you don't have to worry. Toyota is very conservative with their maintenance recommendations...if you follow what they recommend, but not necessarily taking it in for dealer maintenance, you'll be fine.
P.S. For normal driving, GM's oil life monitoring algorithm on Corvettes and my Malibu will routinely show 10-13K between changes for conventional oil or synthetic. For my driving style, I had already convinced myself that 10K was a good change interval based on my own maintenance experience, and GM's oil life monitor confirmed it for me.
P.P.S After 32 years and 178K, do you think I sold the old 4Runner for salvage? Heck, no, it was still going strong, but those major components you mentioned would have made it unreliable for long distances. Those simple old First Gen 4Runners are now SO OLD, they've come back into style as classics. I cleaned and polished it up, and sold it to a happy camper in May 2017 for only about $4500 less than I paid for it originally.
