He's actually pretty good. Hasn't been around long enough to know just how good. Would be nice if he didn't look like such a hobo on the sidelines, but whatever. He's a good coach, in his brief career thus far. If he manages to catch Roma for 2nd, I'll be impressed by that, considering Roma has the superior quality players in my opinion. Need to see more of him at the top level before deciding how good he is.
Spalletti underperformed massively with the squad he has this year. He has one of the best squads in Europe as far as players go, below the obvious top teams like Bayern, Real, Barca, Juve.... Similar level to PSG, Atletico, Chelsea, City, Dortmund, Monaco, etc as far as on paper goes. Lacks a bit of depth is all, though in part his reluctance to rotate and use his depth options is partly to blame there. But finishing 10-ish points behind us, getting knocked out of Coppa by city rivals Lazio, getting knocked out of CL qualifying by Porto, and EL Rof16 by Lyon, is just pathetic. He shit the bed in almost every big match Roma had this season. Poor tactics, easily overcome. Poor subs. Generally looks clueless when things go wrong, and so do his players.