Way back then there were competing visions of what the internet might be - some were corporate (and somewhat based around corporate lock-in) DNA/BNA/SNA/etc others were more com ing from a postal/telegraph sort of world X.25/OSI - in many ways TCP/IP was an outlier, the fact that it didn't really belong to anyone had a lot to do with why it succeeded (also they understood datagrams, and weren't really worried about how to charge for dropped packets).
I suspect (I wasn't even close to being in the room) that freezing TCP was likely a very pragmatic thing, if you wanted to be accepted as THE internet you had to be perceived as finished, otherwise someone else's many 1000 person-year project would have won.
One of the great things about IP is that it's extensible, there's still room for protocols other than UDP/TCP, you can still write something new and better, or a fixed TCP, and install it along side the existing protocols - of course getting everyone to accept it and use it will be difficult
I suspect (I wasn't even close to being in the room) that freezing TCP was likely a very pragmatic thing, if you wanted to be accepted as THE internet you had to be perceived as finished, otherwise someone else's many 1000 person-year project would have won.
One of the great things about IP is that it's extensible, there's still room for protocols other than UDP/TCP, you can still write something new and better, or a fixed TCP, and install it along side the existing protocols - of course getting everyone to accept it and use it will be difficult