No lmao, it isn't leftist. I'd say it doesn't have a lot of politics in it. Fairly neutral, imo.
I used to love it as a child but my family and I haven't watched it in ages, so I haven't been thinking a lot about it and don't have as many fond memories of it anymore. Sometimes thinking about it makes me very sad for some reason (both the show itself and the circumstances around its cast and production). Nowadays I don't know what to think of it. It's definitely not leftist and it was made under a dictatorship, practically. Those were very hard times for Mexican politics. Everybody and their grandma, literally, watched this stuff, so it's obvious that it was used as a way to keep Mexicans distracted through some emotional manipulation (this sitcom got VERY melodramatic in many episodes). And these days slapstick comedy has sort of lost its appeal to me. The cult of nostalgia around this show is also a bit too strong (it's massively popular in all of Latin America but especially in Mexico and perhaps even more in Brazil, where it's known as Chaves).
But I do like El Chapulín Colorado, even though I haven't watched it recently either. Probably because the protagonists aren't kids and the stories aren't sad like in El Chavo.
A bit of trivia. The creator of most of these characters, Roberto Gómez Bolaños "Chespirito" (a corruption of the diminutive form of "Shakespeare") had many other comedy sketches where he played the protagonist. Virtually every single one of them, along with some other characters, had a name that started with Ch: El Chavo, el Chapulín Colorado, Dr. Chapatín, el Chómpiras, el Chanfle, Chaparrón Bonaparte, la Chimoltrufia, la Chilindrina (who was apparently created by the actress that played her, which caused massive drama between her and Chespirito)... I wonder if it has anything to do with him being a Chilango (from Mexico City).