A game that HAS such a button (utilised or not) is "diminished isn't it...
By removing so much challenge from the game - easy money making options enabling ridiculously quick progression to the largest ships, maintenance/replacement costs essentially non-existent...so no problems running or losing ships, no challenge from the AI so combat is more "farming than fighting", easy exploration payouts...so you don't have to even explore to get money/rank etc etc...
It prevents the majority of players actually Playing the Game as hard as they can...its not them vs the Game Universe (which would be ideal) but a kind of mental gymnastics...them vs the Universe with this set of artificial self-imposed rules enforced so as the game retains some challenge isn't it? Which undoubtedly DOES diminish the game and prevent it from reaching its full potential...
Except what you describe isn't difficulty. Credits in this game is entirely an indication on how much free-time you have to blow into making them. While the decisions around the lack of credits/time can be difficult, that's not what makes a game or any task for that matter, difficult or challenging. For example, many people make the mistake of thinking that long or a lot of homework is challenging or difficult. It's not difficult, they just find it tedious. The difficulty really just lies within themselves and it's not truly difficult. Now, there are college courses out there which may truly be difficult and they sometimes even have little to no homework involved. It's because the material, theories and practicing it's applications is actually challenging to many and is what's truly hard or difficult. It's completely asinine to penalize players for not having enough disposable time to grind credits just to play an aspect of the game that they really want to play. For many people, it's getting their hands on medium to large ships as that has always been a classical sci-fi space theme that many sci-fi fans of space games love.
This of course also comes of the realization as someone else said of "who are you to tell me how I should spend my time or what I should/shouldn't be doing?" You're forcing your ideals, playstyle, and false definitions of terms onto others and passive-aggressively debasing them for it.
More players having access to the bigger ships and not caring as much about rebuys as you put it, would actually greatly increase and give the kind of challenge more players supposedly want. What keeps most players away from open is that they can't afford the rebuy or large credit hits on their road to the next thing. With more players out and about with more money, that tends to be more players out and about on open potentially becoming direction competition and an extra challenge that so many supposedly seek. It's kinda funny because many of the people who cried about the fast credits were also many of the same who cried about not enough players in open or even about combat logging. You wouldn't see combat logging as much if credits lost their supreme focus and drive.
There are so many games out there where in-game money isn't the primary factor and players are required to have a lot more skill and in turn, are much more challenging than Elite Dangerous could ever be. We've been seeing this same argument play out since at least Beta because you have those who've made their money or are natural busybodies or self-stylized SJW wannabes who feel that everyone else should play the way they should and see everything the same way they do and will cry and complain till the design team capitulates. I still remember when the traders got extremely butt-hurt when combat jocks finally received pay increases for bounties and FDev eventually nerfed the combat payouts. The the irony was that many of those traders who made it rich trading and maxed out their trade rank and went to do combat then cried when trade missions were making it big and then got those nerfed. Eventually FDev was just forced to increase mission awards across the board in an attempt to make everyone happy but here we are still.
Four years of issues like this comes from the biggest issue of the game where a sizeable portion of the vocal playerbase spends more time worrying about what other players are doing in their own dark corner of the galaxy than they even play the game itself. Even the biggest issues of the BGS that some have sighted being a direct "issue" with these sort of things kind of get shut up when several months of "damage" is more or less corrected in just a few days. These same people btw, who don't seem to care or object with other players UA bombing another player faction's system and shutting them down. I have a feeling that more players would probably rather have a gold-rush in their system than get UA bombed or find themselves directly getting ganked by a concerted effort by several superpowers working together.
Again, credit grinds != challenge/difficulty nor != gameplay content. If someone plays the game to get into a big ship and have fun in it, we as a player base should be all for and in support of that player. So long as that player isn't doing it by directly stealing from the others, who cares? This game is supposed to be about playing the game your own way but there sure as hell seems to be a lot of people these last few years obsessed with only allowing people to play their own way so long as it's their way. Reminds me of the person selling a car and telling the customer that they can get it any color they want, so long as it's black.