Crawl Space - Vent or close and insulate?

[Caleb Fledderjohann]

I just purchased my 1st rental property this month. It's a SFH in Lima, OH. It sits on a crawl space. The inspector report says

"Improper venting was found in the crawl space. This will allow a handle of mildew and mold grow as air cannot properly vent through the structure. We recommend vents be properly installed to allow air flow to move inside the crawl space."

I've been reading online and have found people not venting their crawl space and instead closing it up and insulating it.  Opinions?  Thoughts?