Hi there, I'm in a similar boat as you in terms of experience/speed/age, but I don't fully understand your basic question regarding leg speed. Do you mean cadence (step frequency)? Or something else?
You shouldn't necessarily run at a particular cadence, but it wouldn't hurt to quantify where you're at. The whole focus on cadence in the running world, anyway, is more that it's related to efficiency, as low cadence can indicate overstriding, where you're hitting the brakes with each step. I personally wouldn't worry if you're not overstriding (landing way out in front of your center of mass). This would be more apparent in pictures/videos than any cadence measurement. After all, elites often have a slower cadence than me, but they're running like 80% faster in a given race distance, and they look a whole lot better doing it.
For reference, I'm ~21:00 5k now, and do my easy running at 9:10 to 8:40 pace lately, and my cadence is usually somewhere around 170-175 at that pace. As I get tired when doing faster-paced running, like at the end of a race or at the end of long intervals, my cadence naturally increases to 190+. Last 5k I ran, I started at probably 180 and finished around 190, with a very steady pace. I would say across the board these cadences are all relatively high, especially for my speed and height (6'3"), and thus my range of motion is pretty low. So I've been trying to make a point of running my fastest repeats (like 200-400m at ~6:00 mile pace, striders at sub-5:00 peak pace) with a relatively lower cadence, around 180, to work on opening up my stride while focusing on other aspects of form, like good knee drive and toe-off.
If you do want your cadence to be higher, the thing you can do right now is just run faster - it should naturally increase from the effort of going faster. For example, 200m in about 45-46s, and 400m in 1:30-1:33, using a metronome if needed to hit a target cadence (unless something feels "wrong" when you try it, don't get yourself hurt trying to force a form change!). Get used to that feeling and feed it back into slower paces.
Do you have a watch or device (like Garmin HRM-Run strap) that can measure your cadence so you know what range you're in at different speeds? I've got a Garmin with the HRM-Run, and I can configure it to show my cadence in real time on the watch face. On an easy run, you could start off with your typical running form, then practice gradually taking shorter, quicker steps while not speeding up. But honestly, if you aren't getting hurt, and your form overall is okay, I wouldn't worry about it too much.