I don't agree. I believe that switching is a core tenant of Pokemon, and being punished with what is essentially a free kill if the player switches in at the correct time, one single time, without the opportunity for the other core tenant to me (teambuilding) to support your Pokemon, is broken.
To me, the entire point of 6v6 singles as a competitive game is that you make your team, and you switch around it with strategy in order to wiggle out of weaknesses. The Magnet Pull dynamic to me is just matchup fishing + removes too much control from the other player. If one Pokemon gets a kill, it just dies. If it switches in on the turn the opponent switches in the Magnet Pull Pokemon, it just dies. If the opponent uses U-Turn on that Pokemon being swapped in, it just dies.
Of course, this isn't to say "any scenario where you have to sack is uncompetitive", it's that these are conditions that are too easy to pull off. Usually you get into that position around midgame where you make dents, knock off items, use hazards and status to put your opponent into a condition where they must start cutting their losses. Magnet Pull just puts you, by Turn 1, into a condition where it is essentially a 5v6 game. The moment your Steel-Type does anything that does not involve using U-Turn on the Magnet Pull Pokemon coming in, or killing the Magnet Pull Pokemon, it is dead.
I think that is a bad thing for the game. Magma Storm is much more common so I will use for attacking trapping movesfor why I think it's bad for the game: Simply put it's the same concept. A team will not have several switch ins to the same type (if it is good) generally, and thus an attacking move that traps can put you into a Catch 22. There was a long time (and some still do, IIRC) in SWSH where Toxapex was essentially required to run Shed Tail. The other Fire resists are going to get weakened (say, Dragapult, frail but resists Fire), and Toxapex is often the dedicated pivot, especially for Fire moves. Without Shed Tail, this turns it into a 100-0 matchup, which also therefore makes Heatran much more powerful for the rest of the game.
Simply by being able to prevent the opponent to switch out, you can do absurd shit by just counting and waiting out the chip damage.
Conditional trapping is still bad for the game IMO. Having the certainty that the opponent cannot switch out makes for very bad interactions and makes Pokemon much more powerful than they should be (should, as in, deserving to on outside factors).
Matchup fishing, disgusting sets, gross gameplay.