I hate when fans do this. The only other QB who's even in the same zip code as those two when it comes to throws is Aaron Rodgers. And he's slipping due to age.
Having a QB with an arm like Mahomes and Allen isn't a prerequisite for winning a Super Bowl. More than anything it takes having a heady QB who limits mistakes and makes the big throws when called upon.
If you look at the Super Bowl winning QBs over the last 30 years, it's probably 25-5 in favor of guys like E. Manning, Brady, Warner, P. Manning, etc. over big arm QBs like Favre, Rodgers, and Allen.
Not only that but I'd argue that at least about half of the last 20 Super Bowl winners have been nothing but caretakers/bus drivers.
Dilfer, Brady at least twice in the 2000's, Roethlisberger twice, Eli twice, Wilson, Flacco, Peyton with the Broncos, that's 11 of the Super Bowl winners over the last 20 years.
So it's not even about strong arm/massive arm talent vs. not, you have a great chance of winning as long as you have a QB who can play complementary football and do just enough situationally. Assuming obviously that you have a great defense, running game, etc.
Now, plenty of those winners were going up against non-elite or even average QB's themselves (i.e. Kerry Collins with the Giants, Delhomme with the Panters, McNabb, Kurt Warner in his later years, Cam Newton, Kaepernick, etc.), so it might not turn out as well if you trot out a 2012 Joe Flacco or 2013 Russell Wilson against Josh Allen or Mahomes playing at the level they're playing at right now, but the point remains.