Fanaelialae
Legend
Sure, but I don't see it as a straw man. If you want to run a game with elements of D&D play (like exploring a mega dungeon) plus heist play, which system do you choose to modify? (Also, while it's neither here nor there, I've had people recently try to convince me that D&D is a bespoke game rather than big tent, though I'm not buying it.)Your statement is true, but it only supports a straw-man that the OP put up, it's not relevant to an actual discussion. No one in the real world is picking a bespoke game trying to make it a big tent game. That's just not the direction you take if you are intentionally picking a bespoke game.
Obviously, if someone's already built the perfect system to support everything you are looking for, then there's no reason to reinvent the wheel. However, in many instances, that simply may not be the case. It's easier (IMO) to hack heist rules into D&D than mega dungeon exploration rules into Blades.
It may be that familiarity plays a role in this, but I generally find D&D easier to hack than most games, even when I'm dealing with a new edition that I haven't yet become familiar with. I expect it has to do with bespoke games having a more tightly focused design that is designed to do its intended gameplay well and isn't meant to be tinkered with too much. Whereas D&D has a long history of being tinkered with.