Trocheck is probably better than Malkin at this point, but I still absolutely would not swap the two. Malkin should be the Penguins 2C until he retires, period.
I don't even know where to begin with this because it's absolutely wild revisionist history.
I keep typing up and deleting things like "Goligoski was traded for Neal, who proceeded to do nothing", "Martin and Michalek sucked for the Penguins in their first 2 years here" and "Fleury in the 2010s was just a more durable and likeable Jarry", because there is so much crazily wrong with what you're claiming about that team. I don't even know where to start.
Anyway, the point is that losing a 65 point 2C for a full season isn't going to take this team to a bottom-5 team. Losing Crosby might, losing Malkin absolutely wouldn't.