>they should have caught this 5-10 years ago
They mostly did. They've been warning about this for 3+ years now (see this report from the FCC back in September and October 2019) https://ecfsapi.fcc.gov/file/102214765103/AVSI%20RA%20Interi...
They couldn't have warned folks about more than a year or so sooner than that, because the spectrum bands for 5G hadn't even been fully decided prior to it. (The public notice of band reconfiguration only got announced back in May 2019)