I think there is a lot of detail in this passage about Dr. Shirley that also serves as a foil to underscore Anne's own circumstances.

I am quite convinced that, with very few exceptions, the sea-air always does good. There can be no doubt of its having been of the greatest service to Dr Shirley, after his illness, last spring twelve-month. He declares himself, that coming to Lyme for a month, did him more good than all the medicine he took; and, that being by the sea, always makes him feel young again.

Dr. Shirley's illness parallels Anne's loss of bloom, and his recovery parallels the return of Anne's bloom.

it a pity that he does not live entirely by the sea. I do think he had better leave Uppercross entirely, and fix at Lyme. Do not you, Anne? Do not you agree with me,
that it is the best thing he could do, both for himself and Mrs Shirley?

Oh, this part speaks volumes! First, we all recognize that Anne is better off away from Kellynch, and especially away from her family. The retrenchment, and Anne's stay at Uppercross and her subsequent visit to Lyme, have done her a world of good! The trip to Lyme especially, and the sea breezes, have been attributed as the source of her returning bloom. But also, there is the hint of "life by the sea," which hints at "life with CW." :-)

She has cousins here, you know, and many acquaintance, which would make it cheerful for her

FW has acquantance there, and now Anne may also call the Harville's her acquaintances.

Indeed I think it quite melancholy to have such excellent people as Dr and Mrs Shirley, who have been doing good all their lives, wearing out their last days in a place like Uppercross, where, excepting our family, they seem shut out from all the world. I wish his friends would propose it to him. I really think they ought.

Anne's life at Kellynch has been melancholoy these eight years. And it would be a waste for her to "wear out her last days" in a place like that, shut off from the rest of the world.

My only doubt is, whether anything could persuade him to leave his parish. He is so very strict and scrupulous in his notions; over-scrupulous I must say.