Well, of course you need a DM!
However, I would be hesitant to play in a campaign where all of the decisions you list above are ones in which I, as a player, had no input. Otherwise, what you're saying is that, if I'm not interested or comfortable with any of those decisions, I have to either stop gaming with that DM, or else play along and hope that, in a couple of years when that campaign ends, maybe that DM or another will run something I actually want to play.
And on the DM's side of things, all of that prep and decision-making is being done in the dark. If I'm not getting any player input at that point, how do I know that anything I'm doing is going to result in fun? I.e., will make my players want to show up, keep their characters updated, actively participate, etc?
On top of this, "to take in (as far as possible) only players who will help to make it fun" is a pretty tall order. Wouldn't it be far easier to simply
ask the existing players what they're interested in first?
Vigilance is absolutely correct when he mentions meeting people half way. I'm not saying that the DM has to do only what the players want. I'm saying that
everyone at the table needs to make an effort help each other get what they want.
First example:
One of my groups is currently doing the AoW adventure path. It's not railroading for the DM assume that, yes, we are going to play AoW and not suddenly demand to leave that campaign arc and play
Shackled City. We all agreed that AoW is what we're playing.
Second example:
The same group was discussing some future campaign ideas I had. I posed the concept of running a D&D game in
Ars Magica's Mythic Europe. Everyone liked the idea, but two players had qualms about the existence of real-world faiths in the setting. They're both devout Christians and felt having their religion in a D&D game was inappropriate. "You can keep everything the same, but just call Christianity something else and use a different deity."
So, naturally I... put the kibosh on the whole idea.
For me, making even that small change blew the whole "medieval paradigm" of Mythic Europe, which is the main selling point for me. But I didn't want to offend my Christian players; it's their faith and I respect that. I laid this all out for the group, and they understood my position.
See? I'm not saying the DM never gets to say no. They have a right to fun, too, and what the two players requested messed with the DM's (my) fun. So, I just moved on to the next idea.
Imagine what a total disaster this would have been if I had waited for the "big reveal" of my massively-prepped Mythic Europe campaign on game night. Feelings would have been hurt and no fun would have resulted.
So far, in the couple of years that I have been playing with this group, I've seen that the more communication we have beforehand, and the more we don't pretend metagame issues don't exist, the more fun we have.
Ergo, to get back to the OP... "railroading" has a lot to do with communication. Lay out the parameters for play in advance, and it becomes easier to avoid overstepping them (thereby damaging the fun) during play.