It may be because I tend to DM for new players, but being extremely conscious of the abilities of the characters (and the players!) is absolutely vital to a successful adventure design. Of course, this includes options for teaching moments, situations designed to stretch their thinking and imagination to resolve challenging encounters. And I of course always leave room for them to surprise me, because new players are still players and players surprise DMs, that's sort of their shtick.
I seem to frequently have new players in my campaigns and I love it. I also approach things the AD&D way - which is that I help them with a basic character concept, and throw them in the deep end. The less of the rules they know, the better. We can help them along the way. They don't censor their ideas and thoughts through a filter of how they think the rules work. More importantly, by not knowing as much about the rules, or what the options are later on, they focus their efforts on the character, and how they interact with the world, which provides some stimulus for the direction the character goes in the future.
And really, that's where the difference between min-maxing, munchkinizing, etc. lies in my eyes.
All of the "optimization" approaches are focused on the ruleset. When I see somebody talking about their character "build" then I know they are probably starting with the rules, the abilities, the future options when working on their character. They are looking for combinations and paths that grant them abilities or synergies among abilities. The focus is leaning toward the game, rather than the characters and the world around them.
We prefer to focus on the character, that is, the personality of the character and how they are grounded in the world. The decisions they make based on what the world has given them, and where the adventures lead them. The focus is a bit on the past, and the now of the character, and letting the future present itself, instead of focusing on the future of the character during character creation. They probably have goals, but the goals are based on in world things and almost never about class-based abilities. Sure, a wizard will be looking for new spells, magic items, etc. But they are still based on something in the world, instead of "I want to get this feat, then a dip into this class to get this ability, then..."
Our campaign also has a number of limiting factors built in, that make character building a mix of random chance and player choice. For example, we still have class level limits based on the prime requisite score, as well as minimum abilities required for certain races. We usually roll for stats in order as well. Every player has at least three characters, but a given set of stats may not qualify for every race or class. Since we do character creation at the table, the group can help as well. Of course, some people (like the real world) may choose classes for which the stats aren't "optimal." That's a lot of fun, because it provides some challenges to practice their chosen profession.
By having people start with multiple characters, who come in and out of the campaign, and forcing them to make choices based on "what they were born with" creates quite a different mind-set to building a character. Level advancement is very slow as well, so folks have a chance to build the character, and come up with personalities and approaches that aren't dependent upon gaining new abilities, etc.
On the other hand, I don't design adventures, or the world, with any consideration of the characters and their abilities. If it's a group of all human wizards that decide they want to wander around Undermountain at 1st-level - go for it. The challenge for anybody who is an explorer is to find ways to use their strengths and overcome their weaknesses to overcome obstacles. They know that retreating is a viable (and probably frequent) option. Scouting out and learning about the challenges ahead, to retreat and plan ahead is a common approach. Hiring guides, sellswords, and other help is another option. Sometimes it's just a matter of more characters going out on a particular adventure. They also tend to follow the old-school approach of having a home-base and heading out for a day or two at most, before returning to rest and recuperate.
That doesn't mean that the adventures don't take the characters (or the players) as inspiration for what's going on. To begin with, they are the ones writing the story. And I listen to what they are saying and watch what they are doing, to weave their personal stories into the world. But that doesn't mean I design for their abilities, or lack of.