First of all not every NPC needs to have important information, a lot can know nothing.
How your party behave should also be determined by there alignment. So if your party are good then have a serious conversation with them out of game about there alignment rating and how they should be acting in game, if there is a cleric or paladin then they should, in game, be the moral leaders of the party and if they are ignored then should have agency to act accordingly.
Torture in real life is remarkably unreliable so use this, I have sent parties on many a wild goose chase based on false information provided during a torture based interrogation session. An NPC that knows nothing will make stuff up, you know what they have or have not heard and you can just send the party in the wrong direction then allowing the big bad to achieve there goal.
I would also say that if the party get a reputation for blood thirstiness then good alignment NPCs will be less inclined to want to hire them, so start having work dry up have an NPC tell them that there reputation precedes them and it isn’t a good one. I once had a party who went down this route, by the time they had run around chasing made up shadows, accusing innocents of being bad and torturing and killing anyone that they wanted to question they found themselves declared enemies of the city and where told to leave. The big bad got hold of the weapon he wanted and was to hard for them to kill and there allies all refused to help them. Enemies fought to the death rather then surrendering and insisted on having more support so the enemies they faced where larger and harder and the party cleric who’s god is good alignment found she had lost some access to her powers due to her gods displeasure. Due to all this there experience points started to dry up to.
In the end they decided as a party to work to rehabilitate themselves. They spent a long time improving there reputation and so had a real development moment.
Sometimes you have to remember that this is not a computer game where the world acts in isolation the the players behavior. Every action has a reaction in the wider world. I run my worlds as large open world areas where stuff is constantly happening out of scene that may or may not impact the players experience. If they start going murder hobo they find prices go up, people shut doors, in keepers suddenly have no rooms available, reputation is a big thing.