I find that a lot of D&D players seem to have a fairly mechanistic view of the game, more so than with other games. This is probably a result of D&D, as an offshoot of a tabletop strategy game, being designed in such a manner. Now, your approach is already a lot softer (and I agree that some preplanning is recommended) but the “every party needs a tank, a caster, a healer, a skill monkey, and one of the needs to be the face” I responded to is fairly common in the D&D world.
I don’t agree with that level of party planning. I find it awfully reductionist and belying a mechanistic view on how the game works. I also never found it necessary. Every single element in that list is optional if the players and GM can deal with it. Heck, I’ve never even been in a game with a semi-dedicated healer. For something with clear, limited in-world roles (like your starship example), you do need to allocate them but games like that are rare.
Of course, like I mentioned that D&D’s design informs the way it’s talked about, my experiences are colored by the systems I’ve played, particularly The Dark Eye. TDE affords players much less power than D&D. Spellcasters are much weaker due to slow resource regeneration – they use a mana point system and a high-powered spell will take multiple long rests to recover from. Sure, you can combat heal or throw a fireball but only when necessary. Also, there are way more skills so even with all party members pitching in you won’t have expertise or even competency in everything.
As a result, the idea of having a party that can take on any challenge (and/or deal with several high-stakes battles in a short time frame) is unrealistic. This actually frees up a lot of conceptual space since there’s no one party that can do every kind of adventure. So with some coordination you can make anything work, even a party with no combat or magical skills who Shawn Spencer their way through quests.
What absolutely needs to be worked out are things that could set the party against itself or keep a player from interacting with the others. But that’s more of a player behavior thing; e.g. you can play a perfectly selfish, evil character who still puts the party’s interests ahead of their own – if they’re played to consider having reliable friends worth more than short term gain. So yeah, I also expect a certain amount of character tailoring, just on the roleplay level rather than mechanically.
Some basic discussion of what the adventure or campaign is going to be about is of course necessary. A full-social adventure with a party of dedicated murder hobos won’t work. But if the characters fit mostly within the requirements of the adventure then everything else can be adjusted.
Let’s say the GM wants to do an adventure where the characters will investigate a murder of a member of the city council, which will lead into uncovering and fighting a cult that is infiltrating the city’s upper echelons. The players are only told that the adventure will involve investigation, combat, and high society interaction.
The players come up with a detective, a brawny priest, and a politician who likes dueling. So they’ve got the investigative and social skills, the priest and politician do reasonably well in combat, the priest can even provide some healing, but there’s no ranged firepower and nobody can break into anything. The GM can tailor the adventure to match that; there’s no need for anyone to redesign their character so that the party can engage flying enemies or obtain evidence from a locked room.
Likewise, if the party were to consist of three wizards from the local college, the adventure could still work. One of the players is suggested to hold a teaching position at the college to provide social clout, one should ideally have some experience with investigation or political scheming, everyone is recommended to keep Mage Armor prepared, and the cult now favors ranged combat. The plot might move a bit slower because of less plentiful healing opportunities and frequent rests.
All of this assumes a GM who primarily wants to work with the players to tell a story. If the GM wants to do an unforgiving grind where the players will need to use every advantage (in and out of game) to survive, this won’t fly. Bring an optimized roster or perish. (Of course, most unforgiving GMs I know won’t allow magical healing so that character injuries actually mean something.) I probably wouldn’t join that game but some people roll like that.
On the whole, I don’t find it that goofy when characters die in combat. At least not goofier than when parties always just happen to consist of people whose skills perfectly complement each other, especially ones that form by happenstance.