Sounds oversimplistic. Alas, most slogans and mantras are, can’t be helped.
I think my friend’s point about her ex-husband was that he did change over time. And, I suppose, she did also.
In their case, he did not want the breakup, and tried repeatedly to get her back. But he would not consider personal or couples therapy.
Most of my family are in v successful marriages. And, within those, both parties over time “change” or “grow” or “learn” or whatever. They seem to think it’s part of the job of being married.
I guess the “modern-world interpersonal intimate relationship dynamic” is a little dynamic, at times.