This is really just factually inaccurate though. Modern US liberals are actually further to the left than they were during the bush era, and are nowhere near as far right as the bush administration. (not sure about Reagan because that was before my time but I suspect it was similar). Democrats during that era were just coming off of the very centrist Clinton administration, and have gradually been moving left ever since.
The difference is the people criticizing liberals have become much more numerous and moved much further to the left than core democrats. Which is largely a good thing but I think it would help them be more strategic if they actually understood these things clearly.