There are twice as many blue cards as artifact cards, and basic Island can contribute colorless mana for off-color or colorless spells.
Mishra's Workshop can cast about 10% of Magic spells. Basic island can cast about 20% without any other colored sources, and can contribute mana to ballpark 90% of Magic spells.
Mishra's Workshop obviously casts spells from a radically smaller pool of playable cards.
If you restrict it to just Vintage playables, there are probably 200ish cards you might want to cast off Workshop(s), compared to 1500ish cards you might want to cast off an Island or with the assistance of Islands. Most of the 200 cards Workshop gives you access to are basically available to other decks, so the trade-off is something like "I will give up access to hundreds of cards I might want to play in order to play these 150 cards more easily and have the option to play a few of these 50 cards at all"
If Workshop is restricted, the deck will still be powerful and functional but not oppressive, regardless of future artifact printings. The problem is really the degenerate mana ramp that Workshop provides.
What is degenerate about it?