reviews in "Warsaw In Your Pocket" and "Warsaw Insider" do not always reflect always how everyday people (no expats) experience the city.
How would you know how "everyday people" rather than expats experience the city given than you are actually an expat yourself? As for your comments about the reviews from the Insider, what can you expect from a publication which can't even spell the word "Jalfrezi" correctly and which says that curries "are the right choice" in a particular Indian restaurant.
Interestingly it seems that "everyday people" really do not share your thoughts about The Mexican being "a lovely place full of happy people". gastronauci.pl/5252-the-mexican-warszawa shows that the food gets an average of 1.7 out of 5 and the quality/price gets 2.4 out of 5. And those marks would be even lower if it weren't somebody giving a review that awarded 3 fives for the four review categories! Comments from this year are "Give a wide berth to this place" "Not impressed" and "Strongly advise against".
Even less for the expatists who adore WTF (God knows why, such a pretentious place).
Probably because: the service is good (staff perform or get fired fast); the food is reasonably priced and good quality; when you order "spicy", you get spicy; the cocktails are hugely dangerous; and, unlike every other 'Mexican' or 'Tex/Mex' place in Poland, there is no cabbage anywhere!
People do not need Sense or Tortilla Factory ... They want a place without pretentions where they feel good and at ease.
I can sit in either of those places wearing anything from a plain t-shirt to a suit and feel perfectly at ease. Perhaps your own insecurities are colouring your assessment of places in Warsaw?