Okay, so you're essentially describing a situation where the copyright holder offers access to a "pro" version and a "vanilla" version, with only the latter bei

Okay, so you're essentially describing a situation where the copyright holder offers access to a "pro" version and a "vanilla" version, with only the latter being licensed under the AGPL? I would certainly concede that this scenario would make it difficult for third parties to maintain feature parity, but that's a long way from saying the AGPL offers "no way of competing" with the copyright holder; writing features that are not present in any version would be an obvious starting point. (You also grossly misrepresent the market for "network effects", but that's somewhat tangential)