Does Maatta suck now or am I missing something?
Depends who you ask. He's struggling a little this season, but for some his poor skating (he's slow - or more accurately is slow turning and in his first few strides) ultimately overrides all other factors. On the ice he's usually extremely effective to the point that his skating isn't nearly the issue that some make it out to be. I mean in the POs last season, he was #4 in TOI and only had 2 ES goals scored against him (and 1 should have been blown down on an obvious penalty), and PIT was a sieve goal wise in the POs last season. He needs to be paired with a strong PMD to be at his best. Maatta can move the puck and skate with it... but put him with someone who's better at it then him, and you'll get the best out of him.
As for this deal I wouldn't do it. Not with Addison involved. Even just Maatta for Edmundson would be iffy. Not because of the value (1-1), which I think is fair, but because of the lack of puck movement that Edmundson has. Not saying he's bad, but I think he's worse then Maatta there. Pittsburgh already struggles in this area, and I think Maatta is better at that then JE is. If Schultz was healthy or we had another solid PMD back there, this wouldn't be a concern. But we don't, and thus it is what it is.
In short the only way I'd be happy with OM for JE, is if Rutherford already had a plan to move JJ/Oleksiak and bring in another PMD to pair with Edmunson. But when you hear about how hard it is to make trades... I question how realistic that is.