Hollywood has no concept of what 5th century Romans looked like. If I'm watching a movie about the final days of the Western Roman Empire, I should be seeing zero togas. It's like if you made a movie about the Trump administration, you wouldn't have people dressed like the founding fathers. That's how wrong it is.
This is what 5th century Romans looked like:
I think the problem is that pop culture has this theme park version of history that treats time periods like distinct worlds with no fluidity between them. In Roman Times, people dressed like this vs Medieval Times when people dressed like that. But that is obviously not how time works. The end of the Western Roman Empire led directly into and overlapped with the Middle Ages, and the aesthetics we associate with medieval Europe were already long established.
On a related note, the "barbarians" didn't dress like you think they did either. Less of this:
More of this:
(Art by Angus McBride)
Again, the end of the Western Roman Empire was the beginning of medieval Europe, and it already looked like it.
The notable exception was the Franks, who apparently really did dress like that:
There really is an exception to everything, and it's usually the French.