HIT/HD are good. Over the last 39+ years I have trained volume and Heavy Duty. The first time I tried Mentzer's way was in '77 or so and it didn't work at all for me, so back to volume.
That meant spending 2.5 hours a day (sometimes twice a day) 6 days a week in the gym. That sucks. It also meant eating like every meal was the last supper. That sucks too. A few years ago I decided to give HD another try and low and behold it worked! I began to get bigger and stronger and I was only spending maybe 15 minutes in the gym every two or three days. I had my son help me out and he said it was too much for him to want to train this way. I had a brief but thorough warm up and then did two working sets of two different exercises to total failure and with his help, beyond.
My joints really took a pounding and I gradually modified HD/HIT to fit my needs. I now train between 2 and 4 times a week, up to 9 sets per body part. Sometimes heavy sometimes light, depending upon how I feel. If I need another days rest, I take it! If I need two more days rest, I take it. I listen to myself, my body. Days I feel stronger I put more into it, or so it feels. Other days I train just as hard but if compared to my good days it wouldn't look it. But each time I lift I give my best and always keep in mind to push myself hard, but not over the cliff.
I like doing a single set or maybe two of light weight and high reps (20 to 50) some days. Other days I will do things like negative chins or dips with a weight around my waist. Single reps of negatives five consecutive times followed by those one or two high rep sets and I am done. At this point in my life I may have nothing to prove but I do have something I want to keep. Looking and feeling the best I can via regular exercise.
And a life outside the gym. Mike Mentzer showed us we can have a life and still train hard and look and feel pretty good. My sessions last between 15 minutes and 45 minutes. I wouldn't go back to 2.5 hours a day, six days a week for anything other than having my youth restored.
Once that happened I would resume training as I just outlined.
I hope this proved helpful. All the best!