If I'm running a hotel, for example, my valet has to know how to accomodate old cars and new cars, manual and automatic, electric and combustion, and possibly motorcycles and scooters and such...
If someone comes to the front desk, I have to be polite to them no matter what, whether they look dirty or clean, normal or weird, I can't tell them, your appearance is not good enough, or you don't speak the right language to be at my hotel.
I think the idea of telling the user their browser isn't good enough is the same level of rudeness, it's an act of laziness and arrogance to not even try...
And yes, there are so many different browsers and levels of convenience, and if you want the GUEST to have a good experience, you have to accomodate the shortcomings of their own vehicle, which they may have no choice over, or may even enjoy using and have an attachment to...
The thing I've been working on is mentioned in my profile, the live site is only a few days behind my local dev. Here's a short video I just made with you in mind:) 5igA8Zz56NU