I'd really like to see more mid and high level stuff for B/X in modern osr. Everything seems to be written under the assumption the party is level 1, dies in a single hit, and has no money.
I think this IS the OSR to a degree. That is at least the mid and later periods of it. The aesthetics of both gonzo and grimdark coming to dominate and the real emergence of ultralight system design are both tools to play short high lethality campaigns and sessions. I see this as a response to a couple things that can be summed up as:
The interaction actual mechanics of early D&D-like systems and typical material conditions of play.
That is to say the claims about campaign play first made by Gygax in Strategic Review about 10 hour sessions, 2-3 times a week and campaigns lasting 5 years are simply not feasible for the majority of RPG players. It happens sure, and it worked for a lot of OSR people back when we were kids on Summer vacation too a degree... but I think that the actual higher level content in D&D has to an extent always been either: tournament based, largely aspirational, or accepting of the "Monty Haul" style advancement that Gygax was complaining about as he attacked the West Coast style back in the first year of Strat Review.
The way most people who were really building the OSR in 2012 - 2020 played was in fewer sessions and shorter sessions then the mythic standard, maybe it always has been. This was accelerated by the introduction and dominance of online play. Part of me sees blog and G+ OSR ... the "Renaissance" phase of the OSR that really grew it and popularized it - as opposed to the forum phase of which had a smaller, largely older, hobby shop and long-term campaign base.
Online sessions tend to be shorter (2-4 hours usually) due to the very real "zoom fatigue effect" and while allowing for regularity and more sessions of play also allow for a less consistent player base. I note that the longest OSr campaign I ran the "First" HMS Appollyon campaign ran for maybe three years of weekly and bi-weekly sessions and two PCs who were almost every session reached 8th level, though I believe one of them also played in some other settings from time to time [My forever gratitude to Chris H. and Eric B. - two unsung OSR heroes who play/played in everyone's game they can and always made it better]. The one I played in the longest was four years, again almost weekly with high PC death rates and I had the highest level PC at the end - a 7th level thief who knew when to be an absolute coward (and gained levels faster then the rest).
So my point here is that "high level" play is rare outside the tournament and pre-gen situation and I think it always has been. I mean I once played a PC from 1 - 36th level in BECMI, but I started that at age 11 and well... corners were cut and dice fudged.
Now... there's a second issue.
Assuming you do have a campaign of open world sandbox adventures...
Assuming you have been playing long enough to get the party to "lowest high level" - say 8th level...
How much will they have learned about the world? How well fit into the setting will their interests be? All of those things make it very hard to just drop someone else's content in. This is especially hard as oldschool D&D has been (I think accidentally in a way) adding tools for characters to elide and avoid dungeon risks since day one. At 8th level a good dungeon adventure is a very very hard thing to write or run at least as anything but scene based. If you are running a scene based game it's likely to be intrigue, diplomacy and such - near domain game hijinx with factions, gods and npcs that the party knows and has an involvement with for many sessions. As a designer I can't write that scenario for you in a useful way. I don't think anyone can. Higher level adventures need to be vague enough that the specifics of the setting (even a published one) can be written into the campaign of the referee using it - and it's hard to keep them interesting while making them vague enough to be adaptable.
A tournament module with pre-gens though - Heck ya! I think it would be cool if more people went into adventure design from this perspective honestly. Say a 20 session 8th level adventure that itself becomes a sort of mini-campaign with baked in setting and pre-gens.
[Standing on Soapbox]
I'd like to see more adventures of all kinds really! More innovation in kinds of adventures! Please stop writing hacks and clones people - we need more adventures and you can put your setting ideas, even your hacks and new classes into one!
[Stepping Off]