There's two sides to this. The GRRM problem, i.e. I don't want to get invested in this because it might be left unfinished; and the "holy crap that's too much" problem, i.e. as you say, catching up would require a big time investment. Something like 1316 hours and 32 minutes according to critrolestats. Though the cartoon does condense things down quite a lot. Each dozen or so live play episodes fit into 2-3 episodes of 30 minutes each.
This seems to be a problem like being young too long or having too much money.
Most fans of CR are fans of the cast, not the game. They become fans of the game because of the show. They're far, far more invested in the people at the table and their interactions than the game mechanics. Yes, the one-shots and mini campaigns have lower viewer numbers, but we haven't seen the full cast do anything that's not D&D (afair). The closest we got was Ashley's not-Alien one-shot and it has numbers that every other live play show would kill for.
We have a few examples of them playing non-D&D games ... and there is always a dip in the numbers. Candela Obscura is pulling about a third of what Campaign 3 is pulling - and it has enough of the main cast (with support from tested and known supporting players) to be a fair measuirng stick.
It wouldn't be foreign because the vast majority of fans would buy up the new game really quickly. They'd read it, learn it, and many would play it. It would be new, yes. But it wouldn't be some mysterious, ineffable alien thing. It wouldn't be "foreign" in any real sense.
When we think foreign, we think alien or novel, but the unease of the foreign is not just because something is new. It is because we do not know or trust it. With a new game's rule set, the player base would not feel as attached or trusting. Even the people that knew nothing of D&D before Critical Role now know D&D - and a different system will not be something they understand. That won't be as comfortable. This is one of the driving reasons why they have not been able to generate similar numbers with Candela Obscura, the other rule one shots, or other experiments.
I think you're drastically overestimating the differences between 5E and what we know of the still in playtest Daggerheart game. Everything we've seen suggests rules only slightly lighter than 5E with some more narrative, player-generated elements. Their game isn't going to be "just make it up, LOL."
No, but it will be a different set of rules - and any tweak to a rule set as intertwined as 5E is can have drastic implications. We call 5E 5E - but it is built upon over 20 different rule iterations controlled by WotC/TSR over the years including all of the AD&D editions and half editions, each of the BECMI, DDM, Gamma World, and countless others where they had evolutionary knowledge gained about what worked, and what was a collasal misstep for D&D, even in 4E is a good game in itself for other settings.
Yes, Daggerheart and all the others get to learn from D&D's history as well ... but designing a game as intertwined as D&D is really hard. You may be getting a head start, but nobody has the DNDBeyond Data, the surveys, the playtesting data, etc... that WotC does. We've all seen people take shots at making rules for D&D as their homebrew - and we've seen the huge flaws that those rules create. We see people yell and scream about how broken D&D is in 5E because most people can't understand how well balanced the game is - or see the math behind why. And few that see the math right can see why sometimes you need to twist the math to preserve storytelling options.
Take a look into the history of the 5E stealth system and find the quotes from the designers on why they designed it as they did. Most people that heard it balked at WotC for either being lazy, dumb or cowards in designing such a loose construct. However, if you really think about their reasons for putting so much in the hands of the DM ... it was a great approach to be efficient in rule complexity/length, open ended in storytelling and simplified an insanely complex situation down to something people could use quickly.
If you're into board game design, look into the advice that designers like Rob Daviau ('Father' of Legacy games) have on building games and you'll see why their 40th game is so much better than their 5th ... It is very hard to build great mechanics for a game because you have have to be passionate about what you're doing, but at the same time capable of gutting your favorite ideas because they're great ... but just not right for
that game. Like I said - 4E has fans and I think it is an amazing system ... but was entirely wrong for a continuation of D&D. The 4E designers had the passion, but couldn't see the need to (or wouldn't agree to) throw out their ideas because they abandoned legacy that was essential to the appeal of the game.
I have a lot of faith in Matt Mercer and the people that will be behind Daggerheart. I thoroughly believe that at the end of the day, however, when we have 5 new 'editions' splitting the community, the highest quality game will be D&D. They just have the inside info and resources nobody else does.
