Re: Response time?
Do you believe everything marketing says? Software gets rewritten, just you don't start from a blank screen every time. Large parts of Windows has been rewritten, just not at once.
Anyway, as already pointed out, even re-writing from scratch would have not resolved that issues. This is how SMB is designed to work. If you don't change the requirements and design - probably introducing compatibility issues - code will work the same way. This is not a software bug.
Peer-to-peer authentication implies credentials has to be sent to the peer. Other systems need more actors, and are more complex. Should NTLM die? Probably. The issue is it is too widely used - not only by Windows, think how many systems rely on samba without a windows domain.
It's not that NFSv3 security is far better, for example... and it is still widely used instead of v4 for compatibility reasons as well. Even Apple preferred SMB as the default network file protocol over NFS.
It is true browsers AFAIK don't try to mount an NFS share automatically.