Hard to find doesn't mean cutting edge. TB1 and TB2 devices were hard to find. Firewire 400 and 800 devices were hard to find. ADB devices were hard to find.
And even if TB3 is cutting edge, only supporting it is a stupid move.
NOTHING in current mac products is cutting edge and hasn't been for years. Why would their obscure little port be the one exception?
You do realize TB3 is also USB 3 right? You aren't restricted to using TB3 only.
No matter how you twist it, TB3 is a modern port. Many posters have already stated this and now you're trying to save face.