Can future works sections be similar in different papers? A simple analysis method was proposed in an already-published paper. I am working on a more complicated version of the same method. The future works section of the published paper and my future works section have the same goal. Is it acceptable for both papers to have similar future works goals?
Future work or goals may be broadly similar, there is absolutely no problem there. But if they are identical, the natural question is, what objective does your present work achieve?

You have extended the method (simple to more complicated), so you have already advanced something. Your future work and summary should reflect that - from a writing point of view more than an ethical point of view. If a reader were to only glance at your abstract, conclusions and future work, it should be clear that you have accomplished some goal that was previously unmet.