The speed you'll get on 3G (and probably even 4G) today is much slower than you used to get when those technologies were new.
Also keep in mind that back in the early 3G days your phone didn't send megabytes worth of analytics data. Back then if an app merely tried to access the internet you'd get a prompt enforced by the OS (and probably a bill from the carrier) and so bandwidth was definitely not wasted on analytics and other "growth and engagement" crap.
I suspect the biggest reason for the speed decrease is increased usage though.
Back when 2G/EDGE was current technology I got 100-200kbps there most of the time. Today it is basically unusable as you get timeouts constantly.
IIRC an EDGE Cell could deliver the full data rate to about 8 stations within the coverage area or thereabouts at the same time. This worked okay back then when there were only a bunch of nerds per cell tower using but it can't cope with current usage density and patterns at all.
At least around here (germany had famously high rates for data traffic at the time when 3g was recent) smartphones and data plans are a lot more widespread than a few years ago and usage patterns got more data-heavy as well.