In regards to Muraganda and a vanilla creature theme, sets tend to have only 15 or so cards with any given keyword ability with a few extra cards to support that ability. So, for Muraganda, you make 15 vanilla creatures or so, sets usually have about 5 so you're only increasing it by 10, put 5 more cards that care about vanilla creatures like Petroglyphs, and flesh out the rest of the set with 2 or 3 other mechanics. So for about 20 cards out of 264, not sure what the problem is.
Let’s walk through this. I’m going to talk about this as a limited theme because it’s easier to show the problem.
Players play roughly sixteen creatures and seven spells which means fifteen creatures in the set would have to push heavily towards common to get the as-fan up.
Usually we concentrate a theme in certain colors because it allows us to make less cards of the theme, but vanilla creatures serve a general purpose and need to be in all colors.
We could just push the theme in certain colors and have other colors have the normal amount of vanilla creatures but we’re creating a trap for players unaware of the full content of the set. We don’t usually put one Goblin in an off-color if we have a Goblin tribal theme, for example.
That means fifteen might not be enough and already we’re above the level of vanillas in core sets. We have bigger problems to fry though.
What cards are you going to enhance vanilla creatures with? Creatures? That would make them not vanilla and eat into your viable creature space.
Let’s assume you make them noncreatures. That’s a smaller pool and you still need things like creature removal and other utility cards (card drawing, other permanent removal, counterspells and such).
Let’s say we work all that out. What is the play experience? If you don’t draw the cards that care, you’re playing a game with mostly vanilla creatures. It’s a bit monotonous and is missing important things like evasion to keep games from stalling.
Making you care about a tribe can be fun because we can make a bunch of cool individually evocative cards in that tribe that play fun even if you don’t draw the tribal cards. That’s very hard to do with vanilla creatures.
I’ve just hit the tip if the iceberg. There’s a limit, for example, to how many power points you want to put into vanilla creatures as they aren’t sexy.
And that in many words is why “vanilla matters” is tough to do.
That’s not saying we won’t ever find a way, but it is a lot harder than I think most fans of the idea understand.