I get what you're saying. Favre's system works because the players are drilled and are intelligent enough to play his system. They are also technically decent. Emery hasn't managed to implement a system in six months. Is that down to him or the players? Take Kola for example. He's been good going forward but he's not a natural winger and lacks the intelligence in some situations to do better especially defensively. We also have a few players who are not up to it technically. This makes it hard to play slow as they're poor in possession and not great at moving the ball quickly either! We need to upgrade our squad.Maybe. But it's also of a tactical nature. Emery wants slow build up. That's nothing bad per se, it's e.g. a trademark of Lucien Favre who's tearing the Bundesliga a new one this season with Dortmund. The crux is just how to create space in the final third now that you've pushed the opposition back. Having certain kinds of players certainly helps, but it can be done with average guys as well, something the mentioned Favre has shown at Gladbach and Nice. In that case it's more about implementing triggers and patterns for movement and passing, which is something this team has lacked under Wenger and is still lacking under Emery.
But also looking at Favre again, his slow build up definitely works better the better and more natural wingers he has at hand. But I'm not too sure Emery and Favre is a good comparison bar both using slow build up. Emery seems to tend to a more narrow setup and width mainly provided by the fullbacks, whereas Favre's wingers stay wide until very high up the field.