I think it's important to make things accessible, but that means multiple things and there are many ways to do it....
Say for example in some situations you might slow the power creep but increase the reward, such that instead of having to spam something 20 times as a god you only have to do it like twice but it's still kind of challenging. I also don't mind the idea of aside tools, like maybe you can spend tomestones on echo charms that give you some big boost to echo power. Although another thought is power creep is more to do with survive-ability over damage, so you have more room to make more mistakes but it doesn't really do too much to your damage (meaning you'll still see a lot of mechanics, and certain 'must do' mechanics are still around that area). Perhaps more so in the HP than defense department, so healers still have something to heal lol, though then one may consider some change to DRK anti-buster (else non-whm healers would think even less of that skill lol). Lots of cause and effect to consider when messing with overall balance / pacing...
To me, ... to me.. I am aware some will disagree, I think it's important that over time a huge variety of players can access a majority of the game and in a reasonable format. I believe that is one of the reasons why FFXIV is doing so well, as the game often shows that it knows there is a crowd that needs to be pushed but also spends a lot of time to ensure those who are either time sensitive or not wanting to (or unable, for sometimes legit reasons) cannot perform to a certain level can also enjoy great extents of the game without it being 'work'. A thing that I believe FFXIV does better than WoW, with less FOMO / this game is your work time grinds (at least long term, short term FFXIV may have them but there is a certain group of players that do want ... 'that').
There are a lot of ways to do that though. Currently I do like we have the rolling mountain where it starts more focused to those who play a lot and stay on schedule for their gear, and then difficultly slides down over time, such that you can start to quad, duo, and then even solo old content - and maybe it takes a little while but in general you can envision doing something in FFXIV if you wanted, and given some variable of time, not having to make it your life's work to accomplish that task specifically (and blue mage helps with that too). I would not want to see that concept die, but maybe we can see tweaks here and there to help tighten the sheets on the bed when possible.
When or if the walls to data centers is made more thin it might be possible to have that sort of 'difficultly' system I guess akin to what WoW has, but IMO it shouldn't have different rewards... Just a modifications to the content that they have similar time to reward ratios (so the 'casual DF' would be easier / faster, but maybe you have to do it a few times to get the gear you wanted or to level; meanwhile, in the challenge df things would consistently be hard regardless of gear or group comp, content would definitely be slower due to added difficultly, but you'd not have to do it as many times). I personally don't really buy into the whole difficultly slider should = exclusive rewards thing, just rates that can offset the time investment.
For example many, if not most to my memory, games that are single player have difficulty sliders but you get nothing for making it harder except if that is more 'fun' for you-- I think the whole incorporation of exclusive rewards makes the lower parts of the 'slider' less fun and pushes players to do something they didn't want to do or just not appreciate what they did as much. Of course if you had them exactly the same reward rate but different challenge, since this is a multiplayer game and so time rate is important component, then the people who wanted the top would feel compelled to pick lower for better time value, and this is my point in not introducing systems that damage the choice of how you'd like to enjoy the game. So there shouldn't be exclusives to the 'mythic'+ versions of the same content someone else is running, just a different rate to adjust to approximately make it a similar reward rate for enjoying the game the way you want to enjoy it. I am aware that SE currently handles challenge slider by making new content all together, there are particularly important differences from a slider and new content all together though and is pertinent difference for this thread lol.
(I do appreciate getting to revisit an area, I think it's cool, and I also like the rolling mountain system they've got currently but I do like engaging in ideas to maybe improve while also not damaging other people's stuff at the same time (so making everything harder everywhere, non-optionally, depending by how much, could be a negative to a lot of players- obviously a 1% difference wouldn't really be meaningful disruption but I doubt people here are mentally picturing 1% harder and they're happy). Edit: to incorporate Melorie's post below, I am speaking harder from the stand point of it's currently easy. If you make it so stuff doesn't get so easy, then it is therefore harder. So I see what they're saying but I stand by in essence this will make the game harder if we just instantly hit the game with an anti-creep hammer.