Have you been a wwe fans for long because if your were, i would have known that WWE as always been a babyfaces company. Unless you are in the main event pictures like reigns, strowman, rollins and orton just to name these guys, you will be lose most of your matches as a heel. That's been the way wwe have booked their heels since even before vince jr took over the company from his dad.
As far as tribute to the troops is concern, it's pretty much a glorifiied house show type of booking, it meant to make people happy and that what they are doing with letting the faces win because that's what that audience want to see. That's the old school still of booking.
Let's face it, zayn is a star, will he ever be a top star, no he won't because even through he's great at his role and one of the most over heel they have, he's not going to be believable as a main event caliber star. Ziggler is what i like tp call a plumber, he's a great talent that going to make anybody look like a million bucks but that's pretty much it. He's pretty much this generation's Mr. Perfect. As for nakamura, they tried to push him as a top star and it didn't work, then they tried again as a heel and it didn't stick, they're just something about him that casual fans just don't get and it did hurt his career a little bit.
In the end, the role of the heel is to make the face look good, that's the whole point of a heel especially in the midcard. I think the only problem they have today with how they booked heel is that way to often, they lose clean. They could benefit from going back to making them lose by nefarious means more often, especially on tv and that goes for AEW and other promotions as well. The product is way to clean right now, nobody is taking chance anymore and it's hurting the business as a whole.