Sure, that's a possibility. But when we look at sequels to games that resulted in larger and healthier competitive communities than their predecessors (see SC2, Dota 2, CSGO), the growth of those games corresponded with major growth in the forum hubs of their competitive scenes (TeamLiquid, HLTV.org, Dota's various communities and the new ones that popped up after its success). Those forums grew exponentially alongside the growth of their respective games. The fact that it happened not once, not twice, but three times with three separate games is pretty compelling evidence that people aren't simply replacing forum usage with other mediums.
Compare that growth to the community situation for CoH2. The GR CoH2 portal is essentially nonexistent. The daily active membership on COH2.ORG is a fraction of what the GR CoH1 portal enjoyed. There were regularly 800-900 concurrent users browsing the GR CoH1 portal before CoH2's release; the most concurrent users ever on COH2.ORG is 775.
These other games have more popular streamers with more viewers, better observer functions, and more penetration of services like YouTube. Yet in each and every instance, rather than shrinking like your hypothesis would suggest, growth of these games' competitive scenes correlated with growth of their main forum hubs for competitive play. Looking at forum activity and member numbers, CoH's forum hub for competitive play has shrunk since CoH2's release. It doesn't instill much confidence in the strength of CoH2's competitive scene.
You'd have to compare the overall growth of the forum sites to the overall growth of the communities for the the original game and sequel to compare metrics like that. Sure the forum sites have grown a lot for those games but the community has probably grown by a significantly larger margin.
Coh2 probably does have a smaller overall community, and it has way more games to compete with than vcoh ever did for trying to retain competitive players, so not really a fair comparison there either. Still is interesting to me that some posters in this thread seem to imply that coh2 is a game with a low skill cap that is super easy/lacks competition/no one good plays... Yet we have a consistent top 16 in all tournaments and those making these claims have never amounted to anything on the ladders nor in tournies... Just sayin. (Not really directed at you inverse)