OP here, sorry for late response
It's true that he's never made any IPs, but I think his fame has always come from his directing style. I'd seen Cobra, Treasure Island, and Joe before I learned they shared the same director, but when I did learn it made a lot of sense.
His good stuff always has the nicest balance of attention to character and attention to setting. By that I mean his works are usually stapled by good characters and expert design/style; rather than one or the other. A lot of anime suffer from focusing either too hard on the characters or on the setting. For example, one of my problems with big budget works, like Akira, Vampire Hunter D, and Ghibli's, is that the quality of the plot/characters often trades off with the attention to visuals/setting. For example, many people crap on Castle of Cagliostro because of its take on Lupin's character (lack of character). Miyazaki has never been a master of characters, but of setting, which is why his adaptation of Lupin is known more as a standalone work than another Lupin film. Vice versa, overbearing attention to characters makes a work feel over dramatic /cheesy. For example, if there is too much dialogue/ lack of world building then a work can get stale quick. No one wants to watch a collage of reaction images put over nonstop dialogue.
Dezaki works usually have the perfect balance of well designed characters and great attention to setting. He's got a big knack for atmosphere, usually able to pull off tension, serenity, or whatever emotion he needs in creative ways. I really enjoy his use of backgrounds, especially in Joe. Sometimes he'd use psychedelic backgrounds for neurotic moments, like pic related, and the more well known detailed ones, like the ones you posted, for decisive moments.
One of his drawbacks is that his plots sometimes get ahead of themselves. As you mentioned with Ace there is some BS involving Hiromi. Similarly, in pretty much any of his works, there are moments where if you aren't drawn in well enough you notice the holes (i.e: Joe taking on 5 grown yakuza at the age of 15, Cobra dodging lasers, Hiromi getting good so quickly, etc). Part of this can probably be owned up to the fact that a lot of his works use limited animation, but it's definitely a drawback.