As a scientific methodology, creationism *is* useless.
That isn't to say that Christianity is useless. Clearly, it has great use, in that it shapes the moral fabric of our society and influences our legal structure. It simply is not the proper tool to use, e.g., for investigating phylogenetic relationships of strains of the papillomavirus when trying to determine whether a specific strain is oncogenic.
If we postulate that Creationism is the Truth, then your statement is that the Truth is useless when one is attempting to study Science. I'm sure you wouldn't say such a thing.
To assert what you are saying is to assert that Christianity is useless. Not to mention that the qualifier you’ve added has not been present in the conversation up to now. The declaration that Creationism (Christianity) is useless has been categorical. It’s too late now for a retreat into reasonableness (not without admitting an omission of epic proportions).
But, aside from that, your qualifier remains inadequate still. Absent Christianity, we may expect that the Tuskegee Experiment would have continued to its conclusion with none the wiser and no lessons learned (let’s hope that there have been lessons learned). Absent Christianity, there would have been no careful moral evaluation before E=MC2 was applied to two cities in Japan.
Methodology without morality is lethal.
“That isn't to say that Christianity is useless.”
No . . . of course not. Even in today’s societal atmosphere. Not yet.
Which is why the term “Creationism” is substituted for “Christianity” in so many posts on this forum (the fallacy of the “smuggled concept”). Which is why I spend even some of my time contesting the abuse of the term “Creationism” used in the many attacks launched against Christianity.