Spectrum licensing is more about ensuring exclusive use of spectrum - in a busy built up area (less common during current times hopefully), you'll still suffer from "spectrum suffocation" like with WiFi - if you ever experienced data stalling where your phone indicated a signal, but weren't getting any actual traffic through, you were on a cell that was hitting the limits of the air interface capacity.
The nice part of cellular networks is that you can add more base stations using other licensed spectrum the operator has, in order to get more capacity. So with 3.5 GHz 5G bands, and wider cell widths supported, these can take some of the load in busy places. Otherwise the alternative is to deploy more base stations with lower power on each, to better and more effectively reuse the spectrum.
Since the same operator runs all the equipment on their own spectrum, they can coordinate this much more effectively than ad-hoc multi operator WiFi in a congested area. The downside is the vastly increased complexity of a cellular solution (the sheer number of pages of standards), and the "entrenched player lock-in" available to legacy telecoms operators who already hold spectrum.