I found a couple segments of this to be particularly interesting - you might find the others also interesting.
I'll draw out frame captures of the segments on potential depiction of giants:
Francesco Guardi (1712-1793) - Piazza San Marco in Venice:
Take a close look at the sizes of a few features in the left image (painting) such as the "children" and dogs in comparison to the "adults":
Does Francesco just really screw up the perspective and sizes? Very interesting to think about when I thought that the art of this era very much focused on capturing realistic details...
The right image (modern photo) definitely doesn't have the same problem and it is very interesting that the people are perhaps similarly sized to the children instead.
Now check out the next image in that video, The Arch of Constantine aka "Arc de Triomphe"):
Again, notice the differential of the painting vs an older photo in this enlargement:
Next the video shows an example of doors compared to modern human height standards:
The other parts of the video are not as compelling per se, I especially don't really buy into this modern reset theory or what they're calling the "mudflood", etc. There are too many other options and explanations for far too many of the videos and articles on that topic.