Reddit reviews Introduction to Remote Sensing, Fifth Edition

Well, to come up with my own shorthand definition or contrast of the two, Remote sensing is obtaining or creating data through indirect means of instrument-based measurement while GIS may do some of that but is much more the analysis and processing of said data into useful information and derivative products.

You are correct that fire mapping might make heavy use of both, but there still might be specific position or roles. A drone operator might not touch GIS for much more than AOI (are of interest) and flight path definition. Someone doing fuels mapping based on multi or hyper spectral imagery might spend the majority of their time in non-GIS software, only using GIS to generate some outputs or again with the AOI. A GIS analyst might take some of that information with other sources and then look at how many homes are at what risk, or determine evactuation routes, or just generate maps with boundaries and other information - never touching raw remote sensing beyond maybe some imagery.

This is the textbook from my intro to remote sensing class and this and this are two similar '100 level' books for GIS. You might see if you can find a copy in a local library to take a look at, as even just skimming available chapters and the chapter overviews would give you a fairly in-depth idea of what the differences are. I think if you pick a couple of certificate and degree programs, and then look at the course summaries for what's required you might get an idea of how those tracks differ. I would think you would also have some contacts within your organization you could talk with as far as getting an idea of which skillset is needed for what with how they do things.