Web apps are even worse than cross-platform apps. Nothing scares me more as a future where everything is a web app.
I would precisely challenge the quality aspect here: in my mind the Mac app is so bad that I just gave up on it. To be frank, these are not quality apps in the sense of e. g. Fantastical, OmniGroup’s apps or ProCreate. The iOS app isn’t too far behind: I don’t have a proper, interactive calendar, the layout is just taken from a smartphone and not adapted to a large tablet, I cannot analyze workouts and rides within the app, not even add notes. TrainerRoad’s platform strategy is quite confusing for a newcomer: some features are only available in the apps, other features are only available on the website. The “large” version of the website does not work properly on touch devices, because the touch targets are too small and only “recognizes” the different platforms (Mac vs. iPhone vs. iPad) by browser window size.
Further, I would challenge the assumption that the team is too small. About 10, 12 years ago few friends of mine have a founded a company to bring a professional DJ software to market. (They have received an ADA and WDA, and were featured in multiple Apple keynotes to give you an idea of their pedigree.) They are now offering their software also for iOS, Android, the Mac and Windows, and they surely have a much smaller team than TR. Working with cross-platform code introduces a lot of constraints and friction, especially if you insist on strict feature parity.
What is more, I don’t see bigger companies going away from cross-platform apps. The end user experience is always abysmal, be it that because of that they don’t properly use iOS’s authentication mechanisms (which means that I always need to enter user name and password into my banking apps) or that certain relevant platform-specific features aren’t used. Localization is of non-existent. And TR had its fair share of localization issues as well. @Nate_Pearson said he wished that he had a breathing rate sensor. Guess what smart watch can detect breathing rate 
My Withings scale does not automatically talk to the TR for the same reason either. Sleep information is deposited in Health, too. I’d like an Apple Watch app, too, that e. g. sends heart rate information and allows me to pause and continue workouts, perhaps change the intensity via the digital crown. That’d be a great feature. Or skip songs. Some people would also like to see an Apple TV version — relatively easy if you are native, but very hard if you are not. Another big loss is on-device machine learning, me thinks.
Don’t get me wrong, TR is still the best training service out there and I love the community and the effectiveness. But in terms of app quality, it has a looooooong way to go, me thinks.