So I'm not exactly an expert, I just have some friends who are Swifties and I enjoy sometimes hearing people out about what they're interested in over a beer. But I'll give a shot at answering based on my limited knowledge.
I don't think Swift makes a point out of reinventing herself every time. I guess she had her country phase until Red in 2012 (We Are Never Ever Getting Back Together), and perfected pop in 2014 with 1989 and Shake it Off, Blank Space and all that. The following two albums I know nothing about, but Wikipedia lists them as electropop. And then she completely changes her sound in 2020 with folklore, suddenly being more folksy and reaching an audience of middle aged male music reviewers who had previously not shown any interest in her music. Somehow the fans of her older albums loved it as well, so her fan-base only expanded.
Evermore is kind of a continuation of folklore. I find it to be a little bit more poppy at times, but it's not a huge change of direction, and kind of builds on the same universe (low-key and lower-key). Midnights however, which is her final album to date, is again something completely different: A full blown concept album, and musically again a complete change of direction. A Swiftie friend of mine said she had to give it a couple of spins before she got into it, but that it's now one of her favourites. As a prog rock fan, that sounds about right to me for a concept album.
Personally I started listening to Midnights for the first time ever while writing this post, and I gotta say the opening tune Lavender Haze has some fun things going on in it. The music is interesting, the songwriting is original, and she's a talented performer with a likeable persona. I'm not very surprised she receives her awards.
Why would you think anyone has more staying power than Taylor Swift? At 34 years old she has been in the music industry for 19 years and she's only growing in popularity. She topped the Country charts for 24 weeks with her debut album at age 17.
Sure, we won't be able to compare her to Madonna for another 30 years or so, but I don't exactly see a reason to question her staying power.