When I first read The Sandman, I read them out of order. I read books with Lady Johnanna Constentine earlier than I read Preludes and Nocturnes. I didn't know the character John Constentine until later, and then with the Keanu film, and the (bloody brilliant) Matt Ryan TV role(s). So I'm not bothered that it's not modren John Constentine as such, but I do think it's potentially a little confusing for new viewers that she has the same name and face in both modern times, and in the past.
I know who Lady Johanna Constentine is, and how she is important to the Sandman story, which I think most people criticising her are not aware of her being a character created by Gaiman for The Sandman, as an ancestor of John C, and are just saying "gender swapped, oh it's so woke!!!". In the new TV series it's more confusing because modern Constentine also interacts with Mad Hettie, who is 280 years old, but then at the same time (modern) Johnanna Constentine doesn't believe in Dream of the Endless, at least to start with. But we also have Lady Johnanna Constentine accosting in the pub. Just change her name to a modern spelling. Make 2020's Constentine Joanna, Jane or something, and go with older spelling for her ancestor, when she's in Paris getting a little head (oh matron). But to be honest, keeping John Contentine as John Constentine, and Lady Johnanna Constentine as Lady Johnanna Constentine would have made it clearer that they aren't the same character, albeit they are distantly related.