Spurs under Pochettino had the team that should win at least a domestic cup. Kane big game record maybe questionable, but he scored enough for England and in European competition to suss away the one league bully.
Newcastle at one time was well invested. They did challenge for the league and it's less on managerial brilliance from Keegan, and more to do with how heavy their investment was. Remember Shearer didn't join Newcastle for free or cheap. He joined them for world record fee at that time! Spurs ended up with gold cheaply on luck and they failed to build on it. However, Newcastle and Shearer case is not a David vs Goliath when you applied context.
I am not saying Shearer is bad. He's one of the great no doubt, but he's not someone untouchable. I am saying he had some advantage when compared to later forwards playing in more competitive tactical PL era.