Designated Villain: In several episodes, VENOM's main objective is finding a historical treasure in a remote location, without being a danger to society. However, the show still treats these schemes with just as much urgency as the ones where they do deliberately endanger people, as MASK still attacks them in full force. These episodes always end with MASK getting their hands on the treasure, making it seem MASK is exploiting the hard work VENOM put in their schemes.
Hilarious in Hindsight: The fact that this series based on a toyline by Kenner has many similarities with Transformers and G.I. Joe, was made by DiC Entertainment, and had an episode called "Dragonfire" becomes very funny in retrospect because of the following things that happened afterwards.
DiC produced a continuation of G.I. Joe: A Real American Hero after Sunbow lost the rights to make the cartoon, and the DiC series began with a Five-Episode Pilot entitled "Operation: Dragonfire".
Hasbro eventually bought Kenner and as a result, M.A.S.K. has become a Hasbro property like G.I. Joe and Transformers.
There are now plans for the live-actionG.I. Joe movies and the Transformers Film Series to share a cinematic universe with other Hasbro properties, and M.A.S.K. was one of the properties planned to be involved. Alas, plans to include the property in the universe fell through
The Scrappy: Scott and T-bob are generally seen as annoying by many fans, as they frequently hog the spotlight from MASK and VENOM, while usually not contributing anything useful and get into trouble at least once an episode, requiring MASK to save the duo.
A lot of fans aren't very fond of the second season, where the show was retooled to be about M.A.S.K. and V.E.N.O.M. competing in races.
In terms of the toyline, most fans agree that the Split Seconds line isn't as good as the prior lines. The main gimmick of this line is that one regular vehicle splits into two combat vehicles. While the vehicles in prior lines feel somewhat plausible, most Split Seconds vehicles require much more Suspension of Disbelief to function. The fact that these don't appear in the show also doesn't help in terms of popularity.
Villain Decay: In early episodes, VENOM actually comes off as intimidating, being a criminal group who is perfectly willing to kill innocents to further their schemes. In the Racing Series, they are complete clowns who are literally racing with the heroes.
For the M.A.S.K. comics:
Broken Base: Matt Trakker's Race Lift. Either it's an affront to the character and PC-pandering, or it's an excellent decision to race-lift a White Male Lead since every 80's property in the Revolution (2016) cross-over has a white male lead anyway.
Critical Dissonance: The series is seen by most fans as intolerably bad, but it's won two Glyph Awards and been featured on ComicBookResources' Buy Pile. Go figure.
Vanilla Protagonist: The heroes retread a lot of the standard tropes most heroes tread. This contrasts Miles who was fairly popular by just how integrated he was into the IDW Hasbro universe.
Wangst: Matt Trakker's profile explicitly states that he's insecure and mopey despite being a brave, altruistic, handsome, charismatic engineering genius with the body of an Olympic athlete.
Not surprising, since it was composed by Shuki Levy like many other 1980s themes.