You might think, oh, well its impossible to play that many cards in a single turn, but youd be wrong
Plus, a well-timed counterspell will stop it from becoming a problem in the first place
Focusing on Legendary Creatures can allow players to build some tremendously powerful decks, such as Jodah, the Unifier in Commander, and Annie Joins Up will be right at home in decks like these
For example, it can't be used during the resolution of an ability that says "Counter target spell unless its controller pays 3." If an artifact you control has a mana ability with T in the cost, activating that ability while casting a spell with improvise will result in the artifact being tapped when you pay the spell's costs
It's something we purposefully don't do very often