Aside from some of the other points established in this thread, I feel like the steep learning curve and unforgiving gameplay of RTS', especially those made by Relic are the main reason most people won't stay and play.
I definitely was turned off of vCoH after only a few online matches and resigned myself to compstomps and the fantastic campaigns the first game offered. The same thing happened when DoW2 first launched, and until Chaos Rising came out and I forced myself to play through loss after loss I never fully enjoyed the online scene in RTS'.
These games take a substantial amount of trial and error to find out the nuances and techniques that are required to gain competency and confidence in your play. Your average gamer is not going to jump into multiplayer and suffer harsh losses and still have the desire to sit through 20-40minutes of games and replays, or go online to read about how to improve on their mistakes.
Having said all this, while this game has it's flaws(in design and application) I'm still happy to see it receive success both financially and in terms of increased playerbase. Most games lose players over time, but a jump of 2000 average players in it's second year is somewhat impressive considering the massive amount of flak it has received for (unfounded imo) pay to win allegations and the Russian boycott for the campaign.
True. Had this problem both with vcoh and dow2, started playing, thought that I don't like it, then came back more than year after and started playing for real. CoH2 was different as I bought pre-order (couse I already knew vcoh pretty well) so I played campaign once and then moved to multiplayer.
As for those new 2000 avarage plateyers it was possible basically because of wfa, they opened up on new market of us players who cannot identify with any of basic factions who are still considered as foes in usa. Only the possibility to play usf gave them a chance to play a game for a while and discover what it really is. Then, with some abilities and treating factions as game factions not real life factions they could move to playing soviets or okw. On the other hand lots of them are still playing usf exclusively...