What business does someone who can’t understand gemara have in learning tanya? You can get very confused very easily learning the sefer. It’s not for everyone. It’s not chumash, or tehilim.. it’s a sefer written by an acharon that is no more or less important than the maharal, ramchal, etc…
And ramchal, especially mesilas yeshorim, is a lot more basic and fundamental to learning to live as a functional Jew. So is shaar bitachon in chovos halevavos.
And rambam is not “easy,” it’s learned as a rishon when learning a sugya, but since we often don’t pasken like him lehalacha, it isn’t logical to just learn it straight. If you’re looking for a sefer to amass yedios, then kitzur shulchan aruch is more appropriate.
The Lubavitcher rebbe was wrong to encourage every single illiterate jew who is married to a shiksa to learn tanya – plain and simple.