As a practical matter, I think that you're right — but I think that this is in many cases quite short-sighted of the corporations who choose to go this route, in much the same way that for many years they resisted shipping GPLed software to customers. One can make profit on AGPLed server software in exactly the same fashion that one can make profit on GPLed client software.
If Amazon offered an AGPL Redis, they'd still be able to build whatever they want around it, and keep that proprietary. I'd still find value in paying them for their running-Redis-in-AWS. They'd still make money. Their competitors would get a Redis … the same way that they currently get a Redis.
But antirez and the rest of us would get to share in their performance patches &c. Would that alone make him as rich as he deserves? No, probably not. Would it alone even enable him to make a meager living? No, probably not. But it'd be better than a BSD license, which requires very little indeed.
GPL has neither of these qualities. GPL only requires pay-it-forward with reciprocity being incidental. GPL only prevents takeovers that require proprietization to be effective (which is some portion of takeovers, I'd agree)
Separately, the AGPL situation is obnoxious. AGPL does nothing wrong here. Corporations being anti-AGPL is bullshit (but is indeed all-too-widespread).
You actually don't need all contributors to agree, you only need one. The MIT and BSD licenses don't ban you from relicensing into more restrictive licenses (that's why they're popular with businesses, after all).
The fine hair splitting begins at what is the required amount of modifications required to be able to relicense the given chunk of code.
MIT/BSD is great for small, less important things, and allows for no-question-asked use of such software in basically any setting where software does not need certification. This is something many authors seem to cherish: "my piece is useful and popular!".
The problem is that a small fun hack may eventually grow into an important infrastructural piece, and at best you can try and re-license it under GPL / LGPL if you want more control, and all contributors agree.
OTOH going with AGPL usually means that no corporation will ever touch your software with a ten-foot pole, so corporate contributions to the codebase will be zero (unlike GPL software). This may keep that software more free in one's eyes, but also obscure.