If you asked me what I wanted from a Dark Souls sequel, I'd say leave the formula alone. Don't tinker with what's not broken. Adding all this fast travel and respeccing and voice chat is very much tinkering with what's not broken. Could it still turn out to be awesome? Yes, and it probably is awesome, but cmon. When you tinker with and change core, defining things about the game it's pretty damn natural as a hardcore fan to be pretty nervous.
As one hardcore fan to another, I respect you and your concerns.
But just to address these things that keep coming up:
1. Fast Travel
We're assuming this means you can freely warp between bonfires you've found and sat at. This might not be free at all. You might only be able to warp back to a "safe haven" (even if it's not a hub map like in Demon's). You might not have this ability throughout the whole game. You might miss out on things if you simply warp everywhere. There's so much one can speculate without actually playing through the game and seeing how it works in context.
2. Respec
Again, we don't know the exact details here. We can assume it'll cost a handsome amount of souls, and at this point it reminds me of absolving sin in Dark Souls - something you couldn't do in Demon's - which didn't break the formula or make the game any easier. Savvy pros used the Bottomless Box glitch to "respec" in Dark Souls, but this was abused horribly by less legitimate users. Many of us will still be content starting characters from scratch and trying new builds the old fashioned way, while pros and hardcore players with plenty of souls to spare will be using this new feature to fine-tune their favourite builds or create clever and unique variations that will add to the community (especially important to PvP).
3. Voice chat
Face it, this is just something that thousands of fans (hardcore and casual alike) wanted. Currently, people use Skype and stuff to chat privately, and that won't change. It's been mentioned that you'll need to equip an item/ring in order to use this, so it comes at a cost for those who are desperate for it early on (I actually think it would be a clever idea for a starting gift...) Still, it's another completely optional feature that has no bearing on how you personally wish to enjoy the game at your own pace.
On some levels, I agree with your "if it ain't broke..." mentality. However, it's quite a stretch to say that these things are core to the experience and define the game. The problem is that so many people are looking at
what other games have that Dark Souls doesn't, and using that to define the core. You need to try and look at
what Dark Souls has that other games don't; then maybe you'll have a better appreciation for its design and what's really important here.