I don't really agree with this, especially about Pirate's Curse, going for the achievements like the speedrun and no-damage bosses etc, made me realize the game is actually really well designed.
Shovel Knight does literally all those things better, and I don't personally think achievements are the best way to gauge a game's overall value, They're more a +1 to the main quest. They can draw your attention to what a game does well by imposing a different set of rules, but they don't alter the main thrust of the adventure. If we're talking WayForward proper, Contra 4 is an example of much more robust moment to moment level design, even though it's tough as balls.
By comparison Risky's Revenge and Pirate's Curse are a bit on the shallow side. I'd consider them more akin to something like Monster Tale. Adequate, but lacking depth and nuance. Unless you're a hardcore completionist they're pretty one and done types of games, and even if you
are a hardcore completionist there are games that offer the same extra challenges on top of a much stronger core structure. Not that they're bad games, they just feel kinda cursory, and never really bridge the gap to genre greats. They're like tasty but ultimately fulfilling snacks.