One would think that if the problem is "stuff never gets to come online because campaigns don't make it that far"...
The reasonable choice would be to design games such that most campaigns DO "make it that far", and then provide robust rules for playing at other paces or with other focuses.
While additional rule support that supports higher level play would be welcome: It is not required. You can run successful adventures through 20th level that are exciting, interesting and entirely within RAW.
What
is needed in many groups is training on how to build and run high level games that are not just attempts to "level up" low level games. Even published adventures run afoul of this challenge.
Too many DMs try to run a high level adventure in the same way that a low level adventure is typically built. They present the same types of challenges as low level play and there is frustration because there is magic available that negates the challenges. In turn, the DM negates the availability of the magic. That makes players feel like their choices in development are being invalidated - which is true. The DM, in these instances, ends up dictating the game. That kills a game fast.
A murder mystery works at level 1 or 2 ... but once you can speak with dead, most murder mysteries should be pretty darn easy to resolve. If they're not, it is because the DM is selecting to make the spell worthless in that instance - which feels like a DM taking away a player's toys. That is not to say that being true to the story will always mean a corpse will have valuable information ... just that it inherently feels like the DM is taking away the player tools almost all the time when the corpse does not give up information as the spell is designed to do. A little bit of a player ability being confounded is probably fine ... but if every time you want to use an ability it is negated by the DM because it is too useful - the game crashes.
This type of evolution of the game where challenges become trivial needs to happen. If the PCs have a magical solution that makes it easy to travel, to make money, to help people ... let it happen as a DM. Let them enjoy the free use of their powers. It makes them feel like powerful figures. If they're constantly forced to struggle to do everything they never get that chance to really feel powerful - which is a big part of higher level games.
Then, start to focus on the types of problems that these magics do not solve in one easy blow. An example is a political situation. You have a society of 250,000 people with 75,000 wanting to break up the society and form a smaller society of their own, another 75,000 that want to change the balance of power so that everyone has the same rights and another 50,000 that want the status quo not to change. There is no magic solution that just solves that problem. You can look to books, movies and TV series for inspiration for these types of storylines.
This type of evolution challenges your typical dungeon design. Fighting your way through a 40 room dungeon to get to the MacGuffin at the end does not make sense when the PCs can magically scout it out and then teleport to the end ... unless the DM takes away their toys. To that end, most dungeon delving needs to be rethought and different approaches need to be used, such as anticipate them teleporting to the focal point they need to engage and design the encounters so that enemies come to them in waves while the PCs do what they need to do or wait for something to happen.
Use "Yes and" improve mentalities to make the story work where you build upon what the PCs do rather than negate it.
TLDR: Games work at higher levels when DMs run higher level games that make sense. They fail when DMs try to run low level games at higher levels - and players get bored while the DM is constantly frustrated.