I have been a player in 3 Blades games (2 long term, 1 short term) and ran the game twice (both short term).
The tone of the game, how the ghost field works, what can be accomplished with rituals, what the various factions are like all can dramatically differ from game to game. It's a game without set stat blocks, low resolution setting where much of how things work in the setting can vary dramatically based on the answers players give to the questions you ask or stray Devil's Bargains. Our current Blades game really has a strong focus on the more mystical side, in large part due to a few Devil's Bargains that have brought a Forgotten Goddess into Duskvol. The last game I ran was very gritty, street level and focused on moving drugs (it almost felt like the Wire).
The level of variability there feels pretty similar to my personal experiences with 3e, 4e, 5e and PF2.
See, previously most of these discussions have seemed to involve most people on the “D&D isnt anything special” side claiming that D&D (or 5e specifically) isn’t as broad in what it can do as some other system because it “doesn’t support” anything but combat or whatever.
But, I would be surprised if you didn’t use the procedures of BiTD in all of those campaigns of BiTD, right? Which would mean that you’re still playing criminals of some sort in a dark and grim town, with factions to worry about, dangerous magic, and every scene more likely to further entangle and complicate the PCs lives than not, with a play structure of doing “jobs” with a basic structure.
Because those elements are part of the game’s actual rules, not just genre assumptions and gameplay norms.
Going more mystical is cool (seriously BiTD’s magic is thematically and mechanically very cool), but if you want to use BiTD to play a game where you
defend a small town from bandits, and have to build fortifications, train townsfolk, root out rats, formulate a plan and keep it from the bandits’, and then finally actually fight for the town, you are going to need different mechanics in a FitD framework compared to a
group of knights riding the frontier to protect and inspire the faithful and seek out answers to a mysterious darkness that seems to rising in secret, complete with being empowered and expected to sit in judgement of local disputes.
I can and have run both in 5e, with maybe a page of houserules including the stuff I use for every campaign. The weakness of 5e is that it lacks good advice for DMs on a lot of stuff, and you can’t get
as focused on an experience without heavy DM workload and/or use of 3rd party/homebrew mechanics specific to an adventure or campaign, as you can with “tighter” games that do proceduralize the flow of gameplay to produce a specific kind of game loop.
Point being, Blades in The Dark is pretty focused. It’s a fantasy capers game. Forged in the Dark as a game system ecosystem is very broad, with mostly a type of play procedure in common and some norms and expectations that are shared enough to recognize a fitd game if you know other fitd games.
5e without gutting the PC options and replacing them is similar to BiTD but IMO noticeably more broad without making it a new game. 5e as a game framework (so including 3pp games based on 5e, is more like FiTD as a game system framework.
Tangent:
I’m currently doing prep for a “The Most European Fantasy Fantasy” game inspired by Celtic folklore, Arthurian myth including the chivalric stuff and the earlier stuff, Blue Rose, the works of Guy Gavriel Kay, and a lifetime of loving medieval and pre-Roman and pre-Christian European history and myth.
I may go further than I normally do in changing 5e for this one, like replacing the Spellcasting classes with 3pp options that are less wizzbang, and expanding Inspiration to give players more narrative control. Where the line is where it becomes a new game is something I’m considering a lot right now, because about half my gaming group does not want to learn another new system on top of D&D and my own game. No one balked at flashback mechanics or a “heat die” mechanic to measure and manage devise stress, but if I change how initiative works, now they’re keeping a
third initiative system straight in their heads.