If you really want to be technical about it, the title of the show only promises that we'd get to see how they met. We got to see that, and the entire show climaxed with that nice meeting under the umbrella, and it hammered home that it was destiny. It's not called "How I Met Your Mother and Then Went On to Have the Longest and Happiest Marriage Ever".
And, sorry, while I was going to an extreme example to make a point with The Wizard of Oz comparison- my point is it's not unheard of for a title of a work of fiction to take on a different meaning than what you originally thought it meant. That's just the most famous example. So I just think using the title of the show as an argument against the ending isn't the strongest argument to rest on. Especially when I always saw the title as a bit of a misnomer. So for me FINALLY confirming the title as a smokescreen is what was truly satisfying.
Some say the title was the premise- I say it was the gimmick/MacGuffin. And it was a great hook for the show, but it wasn't the meat and potatoes emotional content. And it could never have been, as the mother is a total mystery for most of the show. End of the day, Ted/Robin was the backbone of the show. I'd go as far as saying that without the "That's how I met your Aunt Robin" twist at the end of the pilot, the show may not have even been picked up in the first place.
That said, I TOTALLY understand why some would feel that it's unfair to the audience that they went to such lengths over 9 years to get them on board with the fact that everything was boiling down to the mother. I get it. There's just a flipside there, in that I felt like they went to such lengths to keep reminding us time and time again that Ted and Robin's story was the central one being told regardless of the fact that they didn't work "on paper". But we all know TV romances don't work logically.