I think the main reason people talk of him being 'shackled' is because it's blatantly obvious he has the talent to be more effective, but we're not necessarily set up to allow for that and that is mainly because of the lack of other options. We didn't hear anyone say the likes of Brown or Long were 'shackled' at full back last season as it's obvious they are defenders first and foremost.
I think you're right that there are manager/system reasons for not getting the best out of him. Robinson's inability to build a proper squad was most certainly the malevolent force you refer to last season and there is a hangover of that on the current squad. Our central midfield last season was Brannagan and McGuane and we were bloody lucky that neither of them were out for a prolonged period.
@Swaby39 has nailed it regarding flogging McGuane to the point he loses effectiveness. He plays a lot of minutes, the only 2 outfield players with more minutes this season are Brown and Moore. I don't think it's coincidence that the more explosive part of his game of driving past the opposition tends to peter out after those minutes start to accumulate.
If we hold Plymouth up as the blueprint for a well assembled squad, then none of their players played more minutes in League 1 last season than McGuane. With a lack of an obvious defensive midfielder, then McGuane assumed that role, something he has been asked to do a bit too much of this season as well. If he's picking the ball up off the centre backs then I think it's unlikely he's going to go driving past people. That's not really a mentality thing in my eyes, more that it's sensible to not try and beat opposition players near the edge of your own penalty area. In that sense I also think the combination with Brannagan as a 2 can be a hindrance, as they're both very good at getting up the pitch but they often can't both do it together at the same time.
It's part of the reason why I'd really like a defensive midfielder in this window. I think Buckingham said his preferred formations are 3-4-3 and 4-3-3 so the second of those would likely necessitate a DM. I also think that would be the formation to get the best out of McGuane where there was a designated defensive midfielder to screen the back 4, leaving both Brannagan and McGuane further up the pitch.
Perhaps you are right there is a mentality thing there with him as well. Often these things are a combination of many things. Perhaps his legs start to feel heavier and then he doesn't fancy it so much? But the talent is quite obviously there and I'd like us to find a way to bring it out more often. In my eyes it'd be absolute madness to just him walk away at the end of the season.
#FreeMcGuane