Where should today's researchers pay attention to 1 _ new research topics suggested from current gaps, or 2 _ revisiting explored and examined topics but in new settings?
There are two research domains where new research topics are coming in two very distinctive ways. The first domain is fundamental natural sciences like physics, mathematics, chemistry, biology, etc. The second domain includes all applied sciences. Within natural science, disciplines that are basic science, also called pure science, develop basic information to predict and perhaps explain and understand phenomena in the natural world. Applied science is the use of scientific processes and knowledge as the means to achieve a particular practical or useful result. This includes a broad range of applied science related fields from engineering, medicine to early childhood education.
Applied science can also apply formal science, such as statistics and probability theory, as in epidemiology. Genetic epidemiology is an applied science applying both biological and statistical methods.
Research topics in natural sciences come from new experiments requiring rigorous theoretical clarifications, improvements and extensions of existing theoretical approaches, or new observed natural phenomena requiring explanations and understanding within scientific frames of reference. Research in applied sciences and engineering caused by practical needs in creating new materials, building new infrastructures, devices, software languages, operating systems, compilers, communication media, etc.
Both are interesting! The advent of new tools has allow us to look back and validate various theories. Research on current gaps and limitations would be most pertinent to what people now. So I would choose the futurlist approach if I have to select. But, for a holistic and sustainable approach, we need both I think.
Research between the past & future is to remain two sides of one coin. Past never remains dead as it gets correlated with the performance of the research, with this future remains the guideline of the factor of the past for the research & whatever the relation of research what we are observing in our life is the guiding factor for the past & future.