Small cars today are huge. I am also 6'4'' and drive a Mk7 Golf. There is more than enough room to get comfortable. Much bigger than my Mk4 from 15 years ago.
I drove a Toyota Matrix for a decade, sure I technically fit, but I spent a LOT of time in it going to sites all over, and any long stretches of time became quite uncomfortable.
Have you ever driven a full size truck like an F-150 or Ram for long distances? It's a whole other experience on your knees and ankles.
I've driven a lot in full size trucks and crossovers and they are quite comfortable but I don't think I would trade the exterior size and poor city maneuverability for the relatively minor increase in comfort I get. I drive 3-6 hours in my Golf to camp and don't have significant discomfort in my legs during the trips. Maybe I'm a freak because I can stretch out my legs in this car while in the driver's seat and get everything down there recombobulated. I would probably be in more pain if I was 15 years older and was driving much more than I do now though.
In fairness to both points of view here, in my 20s it was no problem. In my 40s my knees sometimes randomly start popping when I walk on flat ground in a straight line, lol. This getting older shit is annoying. ;)