For books, this is just plain not true. Generic "buying online" was not huge for Amazon in that year, but buying BOOKS specifically was HUGE HUGE HUGE in that year. And they did in fact sell the 3e PHB a whole heck of a lot on Amazon. It was $20 for a long time there, and they sold gobs of them.
The main point was it was a different time, I have always had 2 or 3 copies of the PHB for example along with some of my friends. We would go to a gamestore and get them, and train people to play D&D. Online shopping existed but it was not so ubiquitous like it is now. I first bought D&D books online in 2004 but I rememebr going to work and the average person had no idea about Amazon or Ebay or things like that.
Remember there was no social media as such either (forums existed) and online gaming was mostly restricted to hard core PC gamers. Xboxlive was in its infancy, PS2 was barely online at that point(1 or 2 games IIRC if that might have been 2005 IDK), and you could go and rent DVD's (no Netflix as such). I had my TV connected to the internet in 2004 (Halo 2) but even then it was not the same as 2 years later when I had Call of Duty 2 on the 360 with things like friends lists.
We bought all our 3.5 books form the local comic book store and later a gamestore (before it closed down). These days I go into a 30 person teamspeak channel and 5 or 6 people play D&D, the younger D&D groups have a PHB each mostly all bought online either Amazon, Bookdepository (cheaper ofr NZer's) and people like using sites like Mighty Ape here which has D&D books, games etc. They did not exist back in 2003 or were in their infancy (technically Amazon had been around 8 years or so at that point). CUlturally people were kind of starting to by online although the trendsetters I suppose were doing that in the 90's (most people were not).
IDK how many copies of 5E are sold in New Zealand, statistically probably not that much but what happens when you apply the same things happening here to Australia, UK and Europe as D&D traditionally has been more USA and maybe UK based. If you are German for example you do not have to track down a gamestore just a couple of minutes online and wait a few days/weeks etc.
Virtual table tops did not exist back then (well maybe they did but once again not that well known/used relative to now).
IDK how many people are buying D&D online now vs back then but I suspect it has increased a lot, we don't even have a gamestore but everyone has 5E PHB (at least those that want them). Apart from postage you can buy them here cheaper than you could in 1995 ($45 vs around $40). Postage usually brings that up to USA non Amazon prices though.
People have gotten a lot more used to buying things online now than in 2003 (and we know 3.5 did not do that well for a D&D edition) so the last time D&D was popular you are looking at 2000. In 2000 you could not really play games online on your TV (well you had Dreamcast which virtually no one had).
5E is the 1st D&D where things like social media, a popular edition, online shopping and consumer culture have converged. Its like someone in 1963 crowing about how good their jet is relative to 1945 or comparing mass airplane transport in 1980 vs 1962. 3.5 was about half as popular as 3.0 and 4E was probably less popular than that once the initial sales surge was over.
Sure jets existed in 1945 a big difference to 1963, same thing with Amazon. Hell when 4E launched Facebook was new along with twitter. Neither one existed when 3.5 launched.
To argue that the gaming environment is not drastically different now is disingenuous at best.