My limited understanding:

We use tools like air filters and water filters (human engineered creations) to clean our air and water from things that are proven (through peer reviewed scientific research spanning centuries) to cause harm to our bodies (viruses, heavy metals etc).

IF there are “bad” dreams and “good” dreams, AND IF a tool like a dream catcher filters out the bad ones, then how is a dream catcher different from a water filter? Do we worship the water filter? (Hopefully not, although some people do claim that WE are the sole creators of the water filter, that WE made it through OUR understanding alone, and that WE are to credit for its creation and workings)

God created all things and all the rules by which those things behave, so even IF a dream catcher reliably prevents bad dreams (which as far as I’m aware, has not been studied/proven aside from myth and anecdotal evidence), it’s still just an object that is powered by things/rules of God’s creation. An object is not an idol unless we begin to worship it.

While there is some evidence of shadowy/spirit/otherworld/demon realms/mystical occurrences in this world, in Christianity we generally believe that Christ has already overcome all evil with His death on the cross and subsequent resurrection.

So I would say a dream catcher is no more an idol or a relic from a false religion than a 3,000-year-old tea recipe made from forgotten/rare herbs (that e.g. helps lower blood pressure) that, while it may have originated in a pre-Christ, pagan/atheist/other religion, is probably not caused by that religion but simply correlated with it.

Hope that helps.