Granted, its non-tokens only, but at minimum creatures that already enter with counters come in with more, and any deck relying on counters (energy, experience, etc.) gets a steady flow of extra counters simply by playing creatures
As of 2025, there are over 289 different serialized cards
For one, it doesn't enter the battlefield tapped, but more importantly, there is an option outside its mana fixing ability
Even if Blightsteel Colossus is countered or would be put into the graveyard through other means, it still gets shuffled back into your deck, making it an unstoppable force that can always come back again
I don't know what your budget is like or if your group allows proxies, but at higher level tables you'd be looking to run cards like Mana Vault and Grim Monolith since those produce 3 mana all on their own
The Rat tokens Vren creates all get extra stats for every Rat, so with just a few removal effects, you'll have an army of Rat tokens that'll be hard to deal with