I just read an artikel that was saying one of the biggest mistakes of Twilight was....

I can't imagine anyone else who could play Jacob any better. To me, Taylor Lautner was the perfect hot-headed werewolf from the books. Like you, I don't agree that casting Taylor as Jacob was a mistake. When the movie trailer for New Moon first released, I recall many fangirls screaming at the sight of Jacob/Taylor taking his kemeja off.
I haven't seen Michael Copon's akting skills, but I can see how he would *look* the part of Jacob. If I had to pick someone else besides Taylor, Michael Copon is who I would go with.

I think Taylor was perfect for the part and he definitely earned it like he had to train suuuuperrrr hard so he could get the part

I remember read many artikel back in 2009-2010 saying that the role of Jacob should have been played oleh a Native American actor... that is the major reason of the criticism over the casting choice. I don't know who could be, though.

I think Taylor was a good Jacob!

I thought Taylor was a brilliant Jacob. But I remember that, back when only the first film had been made, some fan were doubting whether he could bulk up successfully to play Jacob in later films. Obviously they were proved wrong. Maybe that was the nature of the "mistake" this artikel was on about?

The only issue I have with his casting is that Jacob is meant to become really tall. Obviously they can't induce a similar growth spurt in any actor, but there are means to play around with actors' apparent heights (putting them on steps and so on) to make one look like he's the tallest in a scene. I wish they'd done something similar with Jacob, especially in scenes where he and Edward are confronting each other. In the films, Edward is taller than Jacob from what I remember, and that kind of alters the dynamic between them.