Open and close are worth studying.
They’re not optional — they are the path. Everything else grows out of them.
Experiences vary, but the underlying method stays consistent.
Traditionally, until someone reaches a certain stage, true open and true close aren’t available yet.
Their “closing” won’t really close, and their “opening” won’t really open.
Sun style, and Wu/Hao style became known as Kai-He Tai Chi. During this time (in the 1960s), Gu Liuxin invited Hao Shaoru to teach as the 5th major style of Tai Chi, at the Shanghai Sports Hall -- the spiritual center of the shanghai crowd at the time, IIRC. So, these concepts became associated strongly with Hao and Sun style and less so with other styles, who each started positioning themselves as specialist in various things; being good for various things. Even though other lines might not have kept pace with the family. Today, Sun style has special methods to train open and close, as does Hao style, going back to Wu Yuxiang's education in the Chen Village.
You see, open and close are not ambiguous terms at all, but Yang style largely ignores them and holds back training open and close directly in the fundamentals. One of the things Wu Yuxiang did, and Sun Lutang ended up capitalizing on (by bringing in approproate, master-confirmed exercises from baguazhang and xinyi/xingyi) is the large set of open and close material in the jibengong and the long form, exercises he restored to the non-chen styles of the art. Sun Lutang was a minimalist so he presented, I think, three major exercises, with the first one (the most simple one) being responsible for what, 70% of the training? Then the expansion into single whip being the next 25%, and the final 5% are some things you may pick up from brush knee twist step. There are many other openings and closings found there, explicitly, but they are yours to discover after those first three.
For decades as a Yang stylist I didn't really get open and close, even after re-reading Xiang Kairen's work many times. It was only after I learned Sun style that I started getting the hang of it. I noticed that it neatly aligned and boosted what I had already learned in Yang, Wu, and Chen style-- as if it was a missing puzzle piece or air intake valve or something. It was like a second opinion. As a result I came to the understanding that Yang style was a style full of secrets with-held from the players. You can still get very good at it, but you do so with an empty mind through practice alone. I like the extra tips given in other styles. Feels more complete.
I don't thus doubt at all you feel that opening and closing isn't really opening and closing, but I assure you it is well-explained with several direct qigong exercises in Sun style. I hated it when I started learning it, but I tried it and it turns out I grew to love it. Sun style, I reccomend to anyone who does Tai Chi, it is an excellent addition to any style of tai chi.
Tai Chi is one family, all the major styles are exactly the same, just different training methods.