I use the Swagger set, and I initially choose it as a specially defensive variant. I do not use it Swagger set because I like to use annoying or "lucksacking" tactics to win; I use it because I primarily like the Prankster ability to reliably paralyze Pokemon so they can be easier to deal with and its defensive typing. I choose the Swagger set because I can exploit it better than 8 turns of dual Screens (and the opportunity cost of that is no leftovers for Klefki) or Spikes. It is not uncounterable though since a Pokemon like Gliscor will laugh at T-wave and say "thank you sir, may I have another" for Swagger as it doesn't mind hitting itself due to its high physical defenses and welcomes a boosted Earthquake.
I do not feel proud that I won a matches with it because I have residual feelings that it was "unclean" since I felt like I got lucky, and I do not know if my victory reflects a strong tactical sense or just dumb luck. Much planning was involved in the construction of the team and considering many possible situations. But the game relies on luck, even prediction relies on luck too since you are acting on incomplete information about your opponent's temperament, sets, and EV spreads, and your judgment may be wrong because your opponent may be running an unorthodox EV spread or set. It does require some skill to use the Swagger set effectively, since one needs assess the probabilities and choose the best move with it based on the context. The Swagger set is not something one can slap on a team to be effective: for example, I use priority attackers to hedge the risk of using Swagger on physical attackers, and EVed an Iron Fist, Life Orb Conkeldurr so it can outrun base uninvested 50s and positive nature base 115s when Conkeldurr is affected by Sticky Web.
SwagPlay is "uncompetitive" in the same sense as speed ties or missing with hypnosis is uncompetitive. If Klefki hits something with Swagger, it still has 50% chance of getting mauled. It's not a "free +2 confusion with no risks involved," much unlike Moody's "free boosts with no risks involved." The turn it uses Swagger is the turn it is susceptible to being banged up. You can mitigate the damage from Foul Play by switching out your confused +2 Pokemon out, forcing Klefki to risk another Swagger. It's a predictable, manageable, and inconsistent strategy.
Punchshroom, that doesn't change anything what I just said. SwagKey is a risky coinflip, whereas Moody is flipping a weighted coin. Relating SwagKey to something as ridiculous as Moody is a hyperbole.
It is definitely a luck-based Pokemon, but if you do believe that you have favorable odds over the long run, then it is not really luck. It's the same reason why Tony Gwynn Sr. may go 0-4 in a given game, but nevertheless, he was an excellent player compared to other plays who got a base hit in that given game due to his career .340 batting average. It is why baseball teams favor .300 hitters over .250 hitters all else being equal, even though the difference does not manifest itself in a given game. I do not see how this is different from running Focus Blast for a 70% chance to kill a Tyranitar or KO steel types, Lando-T or TTar running Stone Edge to KO Talonflame at full health (or Rock Slide and that works better with paralysis support as a means of exploiting flinch-hax but with lower power in most cases,), or Scald on bulky support water Pokemon. You do need more than on Pokemon to take on ground types when running SwagKeys and (Thundurus-T, Jolteon, and Espeon scare me). The user of SwagKeys has to think like a baseball general manager; one game does not matter, and make peace with the fact you may not get the hax going your way sometimes and that would cost you games. It is best to acknowledge now that the player of SwagKeys is not using it as a means to play psychological warfare or induce rage quits, but a person thinking rationally about the odds.
Jirachi was a stalwart in the Gen 5 metagame, but it wasn't banned due to its notorious flinch haxing.