That's a fair point, but at the same time... as DM, I have plenty to do without holding the players' hands. The only exception IMO is the case where my campaign has an unusual feature which makes normally-reliable abilities ineffective (e.g., a rogue in a 3E undead-centric campaign).
It really is on the players to figure out how to build characters they'll enjoy playing. For all I know, the mounted combat guy may just like the idea of having a knight in shining armor who rides a noble steed, and doesn't care that his mounted combat feats never see use in-game.
If the player is a newbie, some guidance may be in order, but experienced players ought to be able to figure this stuff out for themselves and not depend on me to do it for them. (Or figure it out for each other. One of the advantages of group character creation is that when one player has an idea that probably won't work, the other players are apt to say so.)
If that's the stance, then I'd say I'm on the opposite end of the spectrum, I disagree with the above quite heavily.
I believe in holding the players hands. I believe in shaping the game based on what the players want, and what kind of character they play
tells me what kind of game they want. The game is about THEIR character and if their character can't do what their character is meant to do,
something is wrong.
If they play the mounted knight and are built to use it in combat, then I will go out of my way so that they rarely must go into a place where their horse can't go. Because I believe it's my job as the Dm to facilitate their character and what they want. And if the other PCs say "Hey we want to get on a boat", I'm going to have to put my foot down if it spends too long on the boat, and have a sit-down with the whole group and point out the horse player's issue. Because that's my
job as the GM.
Like Hussar, I don't buy the "Tough noogies". I'm not here to say "here's my game, if you don't like it get the hell out".
There's a system that I really love, called
Fate. In Fate, the big mechanical aspect revolves around a player defining qualities about their character, and when those qualities come up, they get a big boost. The book spells it out: this is the player telling the GM "This is what I want to happen in the game, this is the stuff that's important to me, this is the hell I want you to put my PC through". And if the Gm
does not, not only is he not satisfying the player story wise, but he's screwing the PC mechanics wise. Thus, the GM must serve the situation to the character's purposes, or it all falls apart.
That is how I prefer.