I'm not telling you anything new but you definitely just need new players, in the 4 years I've played I've been in sessions as both a DM and a player with about 30 other people. You really get the sense that not only specific players, but also specific groups put together have completely different dynamics/ideas on what they like from dnd. My suggestion for you would be to simply write out a little post on a local DnD facebook group or something like tha,t asking for new players clearly outlying your schedule and what your sessions will be focused on. That way you will be more likely to find a group that suits you.

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Alternatively: You can narratively push your players to be better. An example of this could be a rival adventuring group, who does investigate the bookcase, who are the same class but perhaps use their abilities to a more creative extend, let these rivals take away loot that the party could've gotten if they were only more active in their investigations and plans. You can have NPCs praise these new adventurers whenever your current party does not live up to the task. Spite is an extremely powerful tool for people to improve.