How does one explore other options while they have a job without exhausting their options and wasting the time of potential employers?

Let's say you have a job you don't love or hate so you're looking around to see if there's anything more attractive. The dilemma I've found is that you may get an interview with another company and it's nice, but not enough to get you to quit your current job. So if this new place offered you a job and you turned them down you'd essentially be wasting their time. Are there any tips to avoid this being a wasted chance and arrange it so that you can be considered later if your current job gets worse and you do eventually want to try for an interview again in the near future? It just seems to me when I try to do this their attitude is basically "You didn't want the job so F off." What is your advice for this scenario? Because at that point I'm more likely to just not even bother looking for other stuff and just wait until I'm looking to quit for sure.

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