The first Morphy game that comes to mind with a closed position was a nice win against Meek in the First American Chess Congress. Although commentators and engines have found slight improvements in Morphy's play, he did a good job of preparing an attack and then breaking open the position with a knight sacrifice.
Improving game from 1400 rating online chess

I think Morphy-without doubt one of the Greats-was not doing so well in closed positions.Nowadays chess is far more open-minded and elastic than in the past and far less dogmatic too.Principles and generalities can have quite a few exceptions and relying on principles is certainly inadequate-if not downright suicidal.The specific is King at chess, which, in the final analysis , is a game played move by move.Even the so called plans may be an illusion.Ideas,yes,sure but plans?What counts is to play a good move on each turn.And that is not easy at all...
Love to see a game that supports this contention.
I agree with the rest of your post. I rather suspect that Morphy would as well.
not precisely sure What the contention is ...
Sorry. I could have been more clear.
Your contention that Morphy did not do well in closed positions.
It is clear that I may be wrong about my claim,after all you know a lot more about Morphy than I do.Harrwitz- Morphy Paris 1858 is a Queen's gambit that he lost as well as the famous 1 a3 Anderssen game but it seems that anyway closed games were a rarity back then and maybe there are rather too few in Morphy's career to judge from.Whatever the case,Morphy was undoubtedly,like Capablanca,a true chess genius.
ok, Ziryab that makes sense.
you are actually much more knowledgeable than most of us about morphys' games. I've heard that said several times (that Morphy didn't play closed positions well)... is it possible that this comes from games that weren't famous?