It's difficult to quantify intensity. My metric for how intense any routine is revolves around any number of factors but are mostly related to how much time you spend at maximum or near maximum output in a given movement, the speed at which you execute and the rest periods between.
Also, what defines a "lap" for that 30 minute interval? You can run for hours on end at low intensity and not work up a sweat or do 30 second 95-100% output sprints a few times with a 30-45 second light jog in-between and sweat your ass off after 10 minutes.
Take any movement - on the retraction I remain controlling the weight on the eccentric and on the extension, pull, push, etc - blast the weight up as hard and as fast as I can. I can move the weight slowly and not try to get the weight up fast, but that small change, despite the same reps, will have an impact on the intensity.
You have different sets of muscle fibers that get worked through the exact same movement depending on how you execute a lift. Hard and fast or hard and steady. Depending on the rep range I am working with I will change the speed at which I execute, the rest periods, etc.
I know people that on their own don't sweat when lifting but when I bring them to my sessions, Niagara Falls.
Timing and effort exerted over that time have an impact on intensity. You can do the exact same movement at varying intensity levels using the exact same rep range and weight.
Or maybe you just stopped sweating. If you're not feeling like you did work - chances are you probably didn't. It should never get easier, IMO.