I have taken some lessons over the last 5 years both in person and online. Some instructors have been better than others. However, I can say I learned something from all of them. Listening to Iacas and Monte on here, and a few folks on YouTube (AMG, Mike Adams and Terry Rowles, etc.) have helped me understand the components of a good swing and what good sequencing looks like. I also have run some things by Valtiel as well. What I would say is that there are some consistent themes I have heard, but each person has stressed something different first and some have been more effective at getting me to change. However, not one of the teaching pros talked to me about how my hips outrace my arms (Valtiel did).
In May, I went to Dan Carraher (iteachgolf on here) as he coaches at a course 20 minutes from me that I used to play all the time. I have known him for years, but he is pricey (and very good imo). He gave me a simple drill, but one that was very hard for me to do. I went out and shot 67 about two weeks later, but I knew I didn't have what he asked me to do ingrained. What he told me helped, but I wasn't "there" and I knew it. I still message him from time to time with progress, but just like the video Monte posted on IG today, I fail the two sequencing checkpoints. 43 years in my old pattern. 2 months into TRYING my new one. I am trying some different drills to get me there in addition to what Dan gave me (I am still doing that several times a week), but I am focused on what we talked about back in May as my end goal. I have a net and hit balls with 9 to 3 swings, slow motion swings, and full swings. I told him ahead of time I was willing to grind away on the work to get there. I was sick of my left misses. Progress is slow, but steady.
In hindsight, if I had seen Dan 4 years ago, I might be miles better than I am now. I think a good instructor gets you to the heart of the matter the quickest. However, it still takes us, the students, to put in the work to understand the what and the why of the changes and spend the time trying to ingrain them.
Just my 2 cents.