I appreciate all that Gavin Norman and Necrotic Gnome have done for the OSR TTRPG scene over the past few years, but I have to say each time I see a D&D-derivative system it makes me wish that other systems of the time—like Runequest, Tunnels & Trolls, or West End Games' d6 system beneath Ghostbusters (1985) and Star Wars (1987)—got even half the attention. Tom Moldvay and Dave Cook's Basic/Expert (1981) has been done to death at this point. For a nice historical lesson, look to Moldvay's later work on the Challenges Game System[0], which pares down the AD&D 1E Players Handbook (1978) into 8 pages suitable for running the game at the table.
I could rant for hours about the sacred cows of D&D deserving slaughter, but I'll refrain.
All this is to say, the Dolmenwood campaign book is great and I own it. It was originally a setting for Old-School Essentials published through a zine[1], and I think they could have stopped at just a campaign book, the one that the OP links to. I just don't think we need any more flavors of B/X!
[0] https://index.rpg.net/display-entry.phtml?mainid=14165
[1] https://necroticgnome.com/blogs/news/the-end-of-wormskin
I am sure those systems deserve a modern renovation, but as a general matter, I think the particulars of game systems matter less, overall, when it is not a mechanics heavy system like Pathfinder and DnD 5e...or Rolemaster. It mostly comes down to rulings over rules...which is why rules lite systems, e.g. Mausritter, Knave, Into the Odd, have play in the OSR/NSR scene.
I do not know where on the crunch spectrum the systems you mentioned fall,
At least BRP (the system behind Runequest) and d6 are actively developed and there are games, new and old, using them. They are also rather popular, at least if one browses rpg.net.
T&T I don't know. I think there is a new edition coming along?
I think one of the impetuses to not using the Old School Essentials rules was the Hasbro DnD debacle where they started making moves to undo the Open Gaming License (OGL) in 2023. The resulting Dolmenwood system cleanly removed the last vestiges of anything that might be subject to the OGL...e.g. certain spell names, monster names, etc.
Whatever the merits of the rules themselves (which I think are estimable), the OSR "ecosystem" is buoyed up by a huge network effect. I would wager that just the list of official D&D modules from the 80s, all of which are easily playable in something like OSE, dwarfs the amount of support that's available for all of those other games combined. That's not counting the many many additional adventures, settings, rules addons, megadungeons, GM aids, etc. that have been created in the last 20 years for various OSR games, which are mostly cross-compatible. It's very hard to come in fresh and compete with that.