If the problems weren't real the team wouldn't have openly admitted it, and confirmed they have a big update planned in that department for later in the year. The team knows it, the drivers know it, ex drivers know it, and journalist and fans know there's issues.
Doesn't mean Meeke shouldn't take the blame for his offs. Portugal was a bad bad mistake considering he was looking good to take the lead on that stage. The 2nd off in Argentina was stupid as well with nothing to gain.
However I still believe the car has superb potential. Despite the engine blowing up in Corsica (something that has happened only a handful of times in Citroën's WRC history), Meeke was pretty comfortable and beating Ogier and Neuville on pure tarmac pace. The car looked great, and as you say he won in Mexico and could've won in Portugal as well...