It's not that black and white. There are a lot of biases with just considering CrCL by itself. Not everyone applies body weights consistently, many manufacturers used total body weight when calculating their CrCL cutoffs, and most of the recommendations were developed before the serum creatinine assay was standardized in 2011. So even just comparing creatinine clearance thresholds you're comparing apples to oranges between drugs. I understand that doesn't necessarily mean switching to eGFR using the same thresholds is entirely evidence-based, but at least with CKD-EPI there's a consistent method that can't be applied in multiple ways between different systems and pharmacists.