I would specify this as being the strongest *mammal* collection in New England. Once you get past mammals, the collection at Southwicks falls flat in my opinion.
Is the deer forest a cool experience? Yes. However it can also be a very risky experience:
Deer injures girl at Southwick's Zoo
I don't think you'll find anyone on this site who will praise Southwicks for its layout, lol. That's one of the zoo's biggest flaws, and one that would unfortunately be difficult to solve without extensive renovations. As for the commercial feel, while I understand that may not be what you or I value in a zoo, that commercial feel is, at least from my experience, the norm outside of the AZA/almost AZA zoos. At least unlike a lot of non-AZA zoos, Southwicks has education as part of its mission and is actively involved in the community as an educational resource. Too many non-AZA zoos ignore this vital role they should be playing.
Honestly, the restaurant is something that I wish more zoos would consider. I would happily pair a visit to the zoo with a nice meal, rather than the way too common standard fast food fare most zoos have. While I agree that Southwicks overdoes the rides and activities, the restaurant is an area I will praise the zoo for.
Thankfully, most of the worst offenders in this regard have already been replaced- with the lemurs and gibbons all receiving new homes. Unfortunately, however, there's still a lot of improvements to be made, especially in terms of how small the holdings are.
Unfortunately, this is a widespread problem, even inside the AZA. I can think of more zoos that flight-restrict macaws than put them in aviaries, and it saddens me that so many zoos (including highly regarded ones) continue to exhibit macaws in this way. There's even a major AZA zoo that's building a new parrot-on-a-stick exhibit this year...