What’s crazy is restricting Mystic Forge and expecting to have any lasting impact. You are band-aiding the real problem in that Vintage manabases are too consistently powerful.
Workshops can consistently drop a 4 CC spell on turn 1/2. Dredge can consistently mulligan to a single card and then hit creatures on its first dredge. Blue can consistently fix a 3 or 4 color manabase with basics. These break fundamental balancing rules that cards are printed with in mind now as none of these mechanics are returning.
What will be printed is another Mystic Forge.
While you’ve provided an explanation, your reasoning is going in so many directions I can’t even follow your logic.
1.) Why would you restrict Narcomoeba? Your primary argument is restricting mana bases.
2.) I am confused by “blue can consistently fix a 3 or 4 color mana base...” If I assume you mean decks that are built primarily using blue cards, I still don’t understand your explanation. Every deck can utilize mana fixing/fetching if needed. If you are specifically mentioning blue because of the powerful blue cards that have been printed, that’s why we have a restricted list. If your original argument is that the restricted list is a band-aid and the mana bases are the real problem, then would it be fine if WOTC printed another Ancestral Recall or Demonic Tutor with restricted dual lands?
3.) That last point bring me to my final area of confusion: to which fundamental balancing rules are you referring?