>>37400092Pretty much all this.
Trade evolutions are a "forced interaction" mechanic; the Pokemon games have always tried to find some kind of leverage to force players to go out and interact with other players, and trade evolution is one of them. The problem is that it instead encourages the most boring interaction of all: "Hey can we trade real quick? I need to evolve this Pokemon."
And that's before discussing people who take advantage of those situations and use it to take other people's Pokemon, which is fucked up. Imagine you had a shiny Haunter, and you had to trade it with a friend in order to evolve it, and the moment the trade is finished, they disconnect. You're stuck with the level 5 Caterpie they had and no way of getting your now-evolved Gengar back, except maybe going to that friend's house and punching them in the face. Great player interaction, GameFreak.