I mean, it's just his opinion. It's based on his approach, his way of seeing, his way of working. What he says is not gospel. But I do consider it, along with what others say. Sometimes different people will say very contradictory things, yet something can be drawn from both. It's common when people give an opinion, they state it as if it's absolute, when we know from experience there is very little that is actually absolute. So one person's words may be used to temper another's, as part of the process of refining our own point of view. Sometimes I've found myself questioning my own thinking because of hearing something I would have once rejected out of hand.
For many years I disliked the 35mm focal length; it just didn't seem wide enough. I loved the effect of my 28, the "professional look" it gave my pictures. Now I look at some of those pictures and they look distorted, and not as pleasing as they used to (just as a lot of the clothing I wore then doesn't look so cool to me now).
I challenged myself to try the 35mm focal length, and see what I could do with it. I bought a Pentax-M 24-35/3.5 zoom and started using it, making myself use it at 35mm, and also observing what focal length or lengths I used most if I didn't pay attention to the zoom setting. I found that I often still settled on 28mm, but sometimes that 35mm focal length was just right, yielding a better picture. I found I had to try new things to get what I wanted with it, and I wasn't just doing things the same way as always. By challenging an old prejudice, my seeing improved, my work improved. I was a little surprised I didn't use the 24mm focal length more, with most work at about 28 or 35.
I do love my 17mm lens. It is a challenge to not make just typical "ultrawide" shots (which I sometimes like to do), but to make pictures with it which alter spatial relationships without it being obvious.
Maybe my outlook has been influenced by my working-world experience. When I started in the golf course business, I didn't know much. I just fell into it; I was offered a job taking care of a small course, and I took it. I started talking to the guys at the courses around, and was amazed at the differences of opinion. The big country club guys all had beautiful courses and strong opinions, but their agronomic practices widely differed and their irrigation practices were in some cases directly contradictory, and yet they were each well-respected and successful. That turned out to be true on the small courses, too. What I realized I had to do was draw from each, and test the advice on my own course, plus my own ideas, until I came up with what worked best for me- and it turned out to not duplicate any one of them! I later found to my surprise that my irrigation technique matched the conclusions of the University of California turf researchers, but if it hadn't I would not have changed because I had found through experimentation what worked best for me. Then came my move to another course, with different soil, different climate, different turf, and I had to change my approach. I was suddenly working to favor the exact type of grass I had been successfully eradicating at the prior job. Later I went to another course with different conditions and had to learn yet another "best" way. Certain fundamentals held throughout, and I guess those could be called my "style".
Cartier-Bresson had his approach and his opinions grew from that; name any well known photographer, and you will find they did what worked well for them, and their opinions will reflect that. Some worked in 35mm, others in only medium or large format. Some in medium format used a Pentax 6X7 or Hasselblad with several lenses; others used a Rollei TLR. Some used just one format; some used several. And each could tell you why.