Yes. 4G can stuff 300% more data hertz for hertz bandwidth compared to 3G. But 5G only does about 15-20% more data hertz for hertz than 4G. It really is a very minor increase in speed. All advertisements about 5G speed are really advertising for limited availability 3.5 GHz and mm-wave deployments in new spectrum... but of course the telcos are now realizing this spectrum, even the half gigahertz they stole of C band, doesn't actually propagate well around Earth instead of straight up and down. If speed alone were the desire, upgrading to 5G standard would not be worth it for anyone. What it does offer is vastly improved minimum latency and easier modularity in network backends.
So realistically, this shutting down of 3G should have happened when 4G came in if speed demands for spectrum were what mattered. But of course back then there weren't enough users to really justify it even if the speed argument applied more then than now.
2G and 3G standards have their place and keeping a 2 MHz channel open for them is not going to get in anyone's way, on the towers, or spectrum-wise.