Nobody is making excuses for Pirri. He wasn't good last year, mostly because he didn't shoot enough. It's not an excuse. It's a thing he did poorly.
The argument that player's are 'bad' because they've played on multiple teams is a bad argument, IMO. Lots of players play for lots of teams. Lots of players get traded because they don't fit in with their current team. Doesn't mean they are bad players. If that's the foundation for your argument (not saying that it is, but it's something that gets spouted here a lot), then your argument is bad.
Again, this is all my opinion.