Regardless of efficiency of the class, I think it's BS that the Monk can't have a grappler build. If their unarmored AC wasn't tied up in WIS, and WIS was limited to saves and some subclass spell casting, they would get more build options, including a high STR grappler.
Other people who don't tend to minmax character builds, but enjoy the round-by-round tactical decisions, and the scope that the monk affords them, seem to be having fun playing them, and therefore don't think that they suck.
My experience is that your round-by-round tactical decision options run smack into your Ki limit.
The idea of switching from tanking to offensive at a moments notice is fun, but I think the value of the versatility was over evaluated. If this was an intent (and I'm still not sure what the Monk was designed to do in the first place) then the Monk should have used a Stance system instead of spending its limited ressources.
Like, every time you take the Attack Action you can change your stance. You could have the Swooping Crane Stance that gives you +2 to AC (like a shield), or a Striking Tiger Stance that gives you more damage to unarmed damage (say, +2, like a Fighting Style).
I think the reason people can enjoy monk and have fun is that when they work (i.e. when they stun something or deflect a missile) they make a splash and are memorable. Everybody remembers their great memorable moments. The Monk certainly has potential for cinematic ones, there's no denying it. The Monk's problems are not those 'highs', it's the 'lows'
between those moments that are lacking. To some people, the highs are enough, to others they just highlight the deficiencies of the lows, and it's just a question of taste what you prefer.