1) Replacing a lot of the running by more shadowboxing/bag work.
Less injuries (I used to run since age 10 up to 25, 3-4 days a week at least), and improved technique (which leads to improved cardio as well).
2) I also monitor my heart rate to be sure I work on the energy systems I want to work on.
So if I want to work the aerobic system (you should have a HR between 70% and 80% of your max HR to do so), instead of going for a 40min 8k like I used to do before, I shadowbox for 40 minutes, non-stop ((my HR is generally around 73% of max HR by doing so, a bit more when I shadowkickbox, with lows around 70% and sometimes peaking up to almost 80%).
If I want to work on the anaerobic system, I do 5 hard rounds on the bag, 1 minute rest between them (I sometimes peak around 90% and go down to 80% sometimes, but I manage to keep it pretty consistent at 85%).
If I want to work on max effort, then I do hill sprints, as it's the only way I've found to spike up my HR that hard.
https://beginnertriathlete.com/cms/article-detail.asp?articleid=3074
Of course I train "normally" without thinking too much about HR and stuff, just doing my thing, and after the training, I look at my Data and am happy when it shows that I worked the energy systems I wanted to work on. But never ever change your style so that it fits your heart rate zones.
Maybe what I do is not applicable to everyone (many sherbros claim they have benefited from running) but for me, running less and doing more of the sport I want to be good at was the best idea I've ever had (but maybe that's because I already had a very solid cardio base).
In the end of the day, you want to train a lot, to be consistent with your training, so it has to be fun. And the funniest thing for me is to work a lot on technique, I could do that for hours. I want to be good in bjj, striking, openwater swimming, climbing, surfing, and I love to work on those skills. Fuck the boring S and C.
Now, if I was a pro, would I have to do S and C? Probably yes. But as an amateur, I'd rather train 20 hours a week always enjoying it and crosstraining a lot rather than only training 12 hours because I'm too bored to do more.