OP, I had a similar experience to you in college - On east days we would just go out and run and maybe do some static stretching after runs if we felt like hanging out together for a while or being around the women’s team. On workout days we’d run a 1 or 2 mile warm up, do some static stretching and some strides, with maybe some of the classic skipping exercises, but that would be about it.
My take on the active stretching and drills that we see more of today is this: the have the goal of activating important muscle groups. I think for someone in your position as a runner coming back to the sport, this is especially important. I think people in their 40s like us are more susceptible to injuries and we can’t get away with some of the flaws in our gait with which we used to be able to get away.
I’m only now starting to incorporate some of these pre-run drills, and I’m starting to incorporate them even on easy days (which is all I do because of a spate of injuries from not doing these things).
My PT tells me I’m not firing my glutes properly when running, so I do glute activation exercises (single leg bridges and similar exercises which I can’t describe). My guess is this is a pretty common area of deficientcy for lots of folks.
Strength training is also pretty important (even if I still ignore it). Unlike in my younger days when we would just focus on hitting the big muscle groups for overall body strength, I think the trend today is to do lots of strengthening of (i) stabilizer muscles like adductors, hip flexors, etc. and (ii) muscles in areas that are susceptible to injury (feet, calves, etc.)
Sorry I can’t be more specific with particular exercises, but maybe the concepts will be a good starting point for more inquiry for you.