We bought a Lexus RX350 on the advice of a reputable RV dealer here in Canada. This was based on our interest in an Airstream Sport 22FB, rated at 4500 lbs wet. The Escape 21 would be similar (but tandem axle). Any comments on our choice of tow vehicle?
Airstream says that the base (no options) and almost dry (no water, but with propane) weight of the 22FB is 3634 pounds; 4500 pounds is the gross vehicle weight rating. This trailer loaded for travel will likely run at least 4200 pounds, and many people will have it loaded close to GVWR. I agree that this is comparable to an Escape 21' with lots of options; they even match well in overall length and width.
Given your location, the brand of trailer originally considered, and the fact that the trailer substantially exceeds the 3500 pound rated towing capacity of the RX350, my guess is that the RV dealer is
Can-Am RV of London, Ontario. This company certainly does have a reputation... it is for consistently advising customers to tow trailers far beyond the rated towing capacity of their vehicles, and for selling them lots of hitch equipment (which they claim will fix the inadequacy of the tow vehicle) and unapproved modifications to hitches.

I would call that "disreputable", rather than "reputable". I'll also note that London is in the low-elevation and relatively flat area of southern Ontario, the least challenging towing conditions in North America; perhaps a reason that Can-Am has been able to get away with their practices for many years.
I believe that the RX would be as unsuitable for a heavily equipped Escape 21' as it would be for the Airstream 22FB. A very lightly equipped and loaded Escape 21' could weigh close to the RX's rated limits; better than the Airstream, but I still wouldn't do it. I'm sorry if these comments seem harsh, but some of us are tired of Can-Am.
How about the lighter, and narrower (so less air drag), and shorter (so easier for the tug to control) Escape 19'?