I see no cause for concern. The Internet can be great for learning and sharing information... But it is a double-edged sword. You see complaints because people take the time to complain. Rarely do people make posts saying "Checking in... Everything's great!".
EVERY brand has had transmission issues, over the years. Transmissions are precision machines, built down to a price, that have to deal with a lot of crap.
You say that Acura has "a good 17+ year history of transmission problems across nearly all models and model years" and yet their reputation is one of QUALITY. Why? Because no manufacturer is perfect, and in the grand scheme of things Honda/Acura does tend to produce vehicles that are better designed and better built than the average. Are you guaranteed to have zero problems? No. Do some people experience unfortunate or even catastrophic failures? Sure. But on average, most people find that Honda/Acura vehicles are exceptionally reliable; so Honda/Acura has that (well-earned) reputation.
Also, keep in mind that Honda/Acura sell a lot of vehicles. The MDX, in particular, has been the best-selling luxury 3rd row SUV for years. How many failures have you read about? What % of vehicles do you think they represent?
Look I'm not disputing they have a reputation for quality. I myself admit when I think of Acura I think of quality and reliability. Same with my wife and her mother, and just about everyone I know. Word of mouth does wonders.
They've done an excellent job of making their brand synonymous with quality and reliability. This is the primary reason why I've looked into the MDX in the first place.
I'm just providing evidence that there are a LOT of issues over the years where Acura had to completely replace transmissions and torque converters. Hence the class action lawsuit and recalls mentioned in the following article. You don't have a class action lawsuit if it's just your lemon here and there, it's indicative of a much larger problem. This doesn't transfer to the new MDX but it just supports the idea that reliability isn't what it once was.
https://wheels.blogs.nytimes.com/2011/01/08/honda-transmission-problems-seem-to-persist/
I'm also not disputing that the MDX is a hot selling vehicle and that Acura has managed to sell a lot of vehicles, they certainly have and a large part of that has to deal with the reputation they've built. My wife's mom has a 2000 3.2 TL and she bought it because "Acura is reliable", yet her vehicle is one of the vehicles covered in the class action lawsuit. Same with my wife's 2001 3.2 CL. Both of them when looking for new cars think of Acura as being bulletproof in reliability because that's what they've heard over the years.
I agree and said that all manufacturers will have an occasional lemon, that's not in question. I'm also definitely not suggesting Acura is inferior to the competition in this regard. Just pointing out that they aren't leaps and bounds better. This is all borne out by Consumer Reports and JD Power's reliability ratings of the Acura brand as a whole and specifically the MDX. Honestly outside of Toyota and Lexus, there really isn't another manufacturer in this segment who's leaps and bounds better than Acura from a long term reliability and quality standpoint. So pretty much regardless of which 3 row luxury mid-size SUV you buy, whether that's an MDX, Q7, XC90, QX60, etc, you're basically in the same boat with questionable long term reliability and quality due to issues reported in the past.
I initially wrote off reliability ratings from Consumer Reports and JD Power of Acura being middle of the pack as being due to a one time flash in the pan issue with the brand new 9 speed transmission in 15/16 (TLX and MDX). There is plenty of evidence to support their broader conclusions on reliability for Acura and the MDX, which they get directly from vehicle owners.
All of this isn't intended to be reasons NOT to buy an Acura or an MDX. From my perspective initially one of the main perceived advantages the MDX had over the competition was perceived quality and reliability. I wanted a vehicle that very rarely needs to go in for service and is almost never likely to experience a catastrophic failure of the engine or transmission. In other words I was looking to buy an MDX and the primary reason why I considered the MDX over the competition is I felt they had the edge in reliability.
My only point is that initially I considered the MDX vastly superior to the competition in quality and reliability, and it was one of the main reasons my search centered on the MDX instead of the competition. I just might need to alter that assumption is all. It's not a reason not to buy the MDX, but it's definitely a reason that I should at least consider the competition as well if every vehicle in this segment in the same ballpark from an anticipated reliability standpoint. But that's all it is: anticipated reliability. No one knows what actual reliability will be like over the next 10 years with the 17 or 18 MDX. They may be perfectly fine with no transmission or torque converter issues and cause Acura to rebound in a big way for reliability and quality ratings. They may not. Only time will tell.