Shovel Knight is a retro game. Betcha never heard of one of those! It's true, Mega Man 9, La Mulana, Retro City Rampage, and Super Meat Boy simply don't exist. You made all of those up in your head. But there's nothing wrong with being the very first game to do what 127 other games have been doing for the past five years. I bought it, so clearly I don't care. And amongst retro throwbacks Shovel Knight has accumulated serious hype for so diligently recreating the presentation and gameplay of classic early-nineties games. Why people get hyped for a game that could've come out in 1990 instead of just looking up any readily available game that did come out in 1990... well, that's what we're here to ask. Because that's exactly how Shovel Knight works: it tricks you into thinking you've played the ultimate classic platformer if you've never played a classic platformer.
What is Shovel Knight? I mean, not just what kind of game is it, but what is its unique identity? How can you tell you're playing Shovel Knight and not Mutant Mudds or Bonk 64? Well, it's a game where the player controls a blue knight wielding a shovel against a world where every knight has an elementally associated X-Men-style unique trait: the one with a helicopter for a head, the one whose suit of armor is a diving suit, the engineering genius, etc. The world is split into platforming levels topped with boss battles which are selected from an overworld map. The player can seek out gold to upgrade their health and magic stores and special weapons to expand their arsenal. The special weapons don't override your main attack and share ammo and can be freely switched on the fly, often coming into play for level navigation.
Shovel Knight stands out against its classic would-be peers in that it has EVERYTHING an NES game might have. It doesn't hone in on the Mega Man boss battles or the Duck Tales collection or the Ninja Gaiden platforming or the Castlevania enemies or the Super Mario Bros. 3 world map or the Kid Icarus upgrading, it just has all of those things. Are we to believe Mega Man 2 was incomplete because it lacked a world map? That the designers left that out because they hadn't thought of it, not because they didn't want it? That Super Mario World didn't add a Metroid element of collection to its exploration because it wasn't a smart enough game? I don't think Shovel Knight is so pointed, but the juxtaposition of all of these elements does suggest such a thought process. Simply asking "why didn't anyone cross over Ninja Gaiden with Duck Tales?" requires misunderstanding that what makes Ninja Gaiden great is that it's Ninja Gaiden. You can't take the gameplay idea and stack ten things on top of it and expect it to still be as good as it was in Ninja Gaiden. The entire concept is born from the modern subtractive notion of evaluation - that every game starts as a 10 and then loses points for what it doesn't have; "no RPG elements - minus one", "no achievements - minus one", etc. It's not that Shovel Knight doesn't have a reason to exist or that its blender-experimentation isn't worth a shot, but the product - a stack of ideas - robs the game of identity and weakens the effect of the elements it does borrow to the point that they simply sit as a reminder that "THIS IS AN INSPIRED GAME".
As a "retro" game I guess you could see it as a triumph that Shovel Knight so successfully mimics the design of the aforementioned classics, as the game could be understood as a meta-commentary on genre the same way Quentin Tarantino movies work without having any identity unique from the history of western/samurai/exploitation film*. It works as a statement that a platformer can no longer have identity because platformers are inherently bound to a time and place and thus the platformer-identity overtakes any unique aspect of the game - that there's no point in attempting a 'fresh' platformer because any such game, without contemporary context, instantly becomes a "new platformer" and is thus relegated to infinite subjugation to a notion of classics, such that the only way for a "new platformer" to succeed is to simply evoke the classics as thoroughly and uniformly as possible, burying itself in the camouflage of homage. Put another way, it's the notion that players and designers are concerned only with stamping ideas, not whether they own them by virtue of creation - "now we have our own platformer". Putting all of the genre classics into a single game relieves the need for experience with the breadth of the field and allows the player, in a single stroke, to think of themselves as a platforming expert. Of course, this is inherently paradoxical in that the triumph of the new game necessitates the supplanting of the old genre, presuming a new farther removed baseline in which the platformer has lost its meaning and function as a stylistic tool and has been reduced to a simple pastiche with genre itself as the ideal - where there exists no platformer whose purpose is anything but to be THE platformer. It's in some sense an encapsulation of genrefication as a whole, particularly through the lens of a mainstream removed from the time in which the original explosion was relevant.
Of course, the premise of Shovel Knight viewed thusly marginalizes genre fans - it is a platformer for those uninterested in platformers, existing solely as a reductionist novelty.
* I realize not everyone shares my take on Mr. QT but it's a catchier premise this way.