"They flee from me who sometime did me seek
With naked foot stalking in my chamber.
I have seen them, gentle, tame, and meek
That now are wild, and do not remember
That sometime they put themselves in danger
To take bread at my hand; and now they range,
Busily seeking in continual change."

Ok, I get it: he's not getting the babes he used to.

"Thanked be fortune it hath been otherwise / Twenty times better..."

I'm with him so far. But then the poem shifts gears: "But once in special / In thin array after a pleasant guise / When her loose robe from her shoulders did fall / And she me caught in her arms long and small." Now he's talking about one particular woman.

In the third and final stanza of the poem he lays on the irony pretty thick, with "gentleness," "goodness," "kindly." "We are both free to see other people now," in modern parlance. Now the poem has shifted into a complaint that this particular woman has left him. Was this the point all along? Then the inconstancy of which he complains makes no sense, in relation to the beginning of the poem. What he conceives of as "newfangleness" or "continual change" was always so: the illusion that the wild animals / women were tame was just that, an illusion.

Wyatt seems to like abstract nouns. I do too.