I've only played the game a bit, but I tried all the minigames from the main menu expecting the worst and... I don't really get the huge criticism with them? Some could be more polished (Bee Bop's animations and physics) and Hurdle Hijinx seems to be quite hard, but I can't see them as the bad aspect of the game and game breaker that people are claiming they are (they need a retry button, though, that's for sure). I really liked Kartos Karting*, Up'n Nova and Jobstacle Course, and while others like Glaciators and Blag the flag are pretty weak and clearly oriented to multiplayer, most of the others are well done.
However, I can understand that some of the required scores are too high and that some minigames are too long. Minigames would probably be better received if they were shorter and each one was segmented into three difficulty levels. Playtonic could easily take a minigame like Hurdle Hijinx and split it into three shorter levels (en easy one taking the first segment, a medium with the second segment, and a hardest one with the final segment where everything goes crazy). You could get the first pagie completing the easy one and the second pagie completing the medium (and leave the hardest for pure completionists). This could actually work for Hurdle Hijinx, Up'n Nova, Jobstacle Course and Gunlet Run.
*Regarding Kartos Karting, it obviously has a rough control, but that's exactly the idea. If you could drive this thing propperly I would find it pretty boring, and honestly it isn't that hard to master. I got the two Pagies at my second and third try respectively.