I here you.... I am kindof in the same position, but I really like intervals, as easy or moderate running is not giving back any "energy".
I have been training too intense for long periods I believe it is not easy to actually feel that on the body, but the results are not better. I have read about people that excell after injury so enough recovery both in short and long term is maybe hard. I am also more scientifical in the approach (and I really dont think "common sense" is an alternative)
All training is a mix of what have been and what is and it is really hard to with you say anything conclusive. Does the prior training model work? Well, with the volume you lay down, it did not work then, but now when you do less intensity, you excel. Is it because of the new or because of the combo with the old?
I listened to a runner that could train hard and recover fast, but he used the word optimal and not maximal. We are many motivated to run as much as possible to improve as much as possible, but a lot might not be the optimal to improve a lot. I came back after low years in the spring 2019 and improved for 9 months. Then I have basically for 2 years now NOT improved.
So the focus for me will be how to find the optimal. I have so much motivation for both volume and intensity and it will be hard to having to reduce to improve. Strange since it should be obvious.
After summer I changed my ways some and cared more about recovery at least to recover to fresh legs each second week. I did some testing every 14 days and improved for a long time. Then I got som problems with consistent testing so I have not done that for a while, but, I improved. I will continue to follow those ways, but focus even more on actually respect the recovery needs. There is no payback from hard training if not recovering from it as improvement happens in the recovery and not the training.
This is hard since my head hears and thinks more is always better.
For you I don't really think the model with moderate is the reason for your improvement, I think it is in the totality. I would go scientifically onwards and try to balance the right stimuli for you and the right amount of recovery to excel from it. Presonally I don't think hard intervals are good for long term improvement, especially when you run 10k and M. Try intervals in the range from M to HM. If you think your VO2 max is not well developed (which I doubt given your PBs) do some hard stuff,