ZeshinX
Adventurer
That's always a good idea. I dont think this a case where it was the issue though. I've had that conversation with DMs and when it sounds like that it's almost always plot point related. That's why prescripted plot without flexibility can make for an awkward game.
That's a conversation I have with my players before any campaign starts. They know my style in that I like to have a pre-scripted plot, so we discuss it early so they can offer suggestions for their characters that might be useful to work into said plot. They don't get details of said plot, but offer interesting things they'd like their characters to do, or interesting aspects related to their characters they'd like to explore. So they rely on me to find interesting ways to take those suggestions and work them into the plot, to whatever degree makes sense (they allow for me to manipulate suggestions so long as it hews close to their desired intent). That way, they don't get too rankled about the game feeling overly railroad-y, and as often happens, makes me change my plot for the better.
Some moments still occur where it seems like I'm being somewhat unfair or NPCs seem overly protected with plot armor, but they do understand it's not a "forever like that" state of affairs. They do still tease the hell outta me for it, but we all recognize it as necessary and constructive (and fun!) venting for moments they feel reek a tad too much of DM abuse.
I've also made strong efforts to highly minimize moments like that and roll with whatever wild and wacky "solutions" the PCs might dream up...mostly in the form of trapdoor options for when actions by the PCs take my written plot elements and wipe their metaphorical bottoms with them.
In that particular example by the OP, I'd likely have let the PCs succeed...the cultists return to their master, get absolutely chewed out for being so susceptible to such an "amateurish" tactic, then sent on one final test to prove their value to said master, probably in the form of some kind of ambush, with any subsequent failure being punishable by death or implied threat of death (so they have at least a plausible reason to not be susceptible to any lower-levelled mind affecting spells of effects). I'd roll with it from there...the cultists might get slaughtered...the PCs might somehow find a way to turn the cultists against the master, etc.