Saying landing in thunderstorms yes or no is far to black or white.
I generally steer clear of active CB's.
However I have landed in reasonably bad weather within Europe and although operating at an increased level of alertness, with a possibly amended approach, I have never felt, few only just got away with that!. If I waited for every thunderstorm or CB to move away from the airfield I would be "holding off" frequently which is a poor balance of risk. Also although from the ground the cells may seem well spaced I am sure many pilots will agree that even at the slower operating speeds finiding a bit of clear air to "hold off in" in already crowded airspace is not always easy and not without risk.
There is a lot of info about CB's and thunderstorms and put together with experience you get a feel for what is and what isn't acceptable.
I certainly wouldn't want to fly an approach through a super cell!!