That’s ignorant of modern scholarship. Here are some serious historians you might want to look into:
- Peter Heather
- Anthony Kaldellis
- Averil Cameron
- Timothy Gregory
- John Haldon
There are others, of course.
And no. By the time the Western half collapsed, the East had not drifted apart. That started happening 2-3 centuries later, definitely after Justinian. And it was not even completed as a process until after the 4th crusade at least.
Honestly you are right as someone who started his love for history with the Romans, I didn’t know this was a debate, so I did some research and to me personally the end of the Roman empire was 476ad with the last western Roman empire abdicating. Or perhaps the fall of Constantinople