You make some valid points, but the evidence is much stronger than you seem to think. The Native Americans attributed the supernatural and their spiritual beliefs to every animal they were familiar with, including wolves, bear, deer, crows, turtles etc... That in no way can be used invalidate hundreds and potentially thousands of years worth of Native American legends of these creatures.
I understand that eyewitnesses can be unreliable. But we are talking over 10,000 eyewitnesses across a time frame of hundreds of years going back to at least the time of Samuel de' Champlain. Surely not all of these eyewitnesses are hoaxers, liars, or misidentifying "normal" animals. That would be even more incredulous and would stretch the imagination even further than supposing Bigfoot exists.
Footprints can be faked, but by and large the hoaxes are easily identifiable as such by trained investigators. Grover Krantz even offered $10,000 cash to anyone who could fool him with a fake track. Needless to say the cash amount had no takers. Track casts with dermal ridges and a mid-tarsal break are outside the scope of ability of most hoaxers with their plain wooden stompers. Add to this the remote and inaccessible locations of many of these track finds, and the probability of them all being hoaxes diminishes significantly.
The Patterson-Gimlin Film is the Holy Grail of Bigfoot evidence, and perhaps the single strongest piece of evidence for the creature's existence. Till this day it has never been debunked, and no one has convincingly demonstrated how such a costume could have been made in 1967. The technology to make such a costume didn't exist in 1967.
So your assumption that Bigfoot doesn't exist is more unlikely and indeed more difficult to prove than the inverse.