Why is polyester hydrophobic as well as insoluble in various organic solvents?

Polyester is known to be hydrophobic as shown by it's low moisture regain.


However, esters are at least somewhat hydrophilic and soluble in water. This decreases with the hydrocarbon chain length increase, but in the case of polyesters, this is accompained with a proportionate increase in the number of ester groups.


My attempts to explain this were as follows


1. The reason nonpolar molecules are not soluble in water is the H-bonded structure of water is disrupted - there's a loss in entropy; water molecules have to orient themselves in the form of a cage around the non polar regions.


In the case of a polymer chain of PET, the loss in entropy is greater than if we tried dissolving the individual monomer esters that constitute it in water. Therefore one is somewhat soluble, the other is not.


2. Since like dissolves like, and a polar aprotic solvent would not have the H-bonded structure of water that would be disrupted (and in fact since they are both polar aprotic, one would presumably become well incorporated into whatever bonding structure the other has), I would think a polar aprotic solvent would dissolve polyester.


Turns out that this isn't the case. In fact, "polyester fibres are generally resistant to organic solvents" (A. Bendak and El-Marfasi; [pdf link](https://www.google.com/url?sa=t&source=web&rct=j&url=https://jag.journalagent.com/ias/pdfs/IAS_4_4_275_284.pdf&ved=2ahUKEwiAir2T5d37AhWEeN4KHSPpAhcQFnoECAkQBg&usg=AOvVaw3sg51EkbnIfegmqv8ih5YN))


Perhaps, I thought, this might be because of the relatively crystalline structure of polyester that doesn't allow solvent molecules to penetrate it below its glass transition temperature.


However, polyester fibres are soluble in phenol and m-cresol. They [here](https://www.researchgate.net/figure/Relative-solubilities-of-Polyesters-in-different-solvents-at-30-o-C_tbl2_286892808) also appear to be soluble in THF and DMF, but not the remaining organic solvents.


Why wouldn't the same issues that were occurring with water occur with these polar protic solvents (phenol and m-cresol), and why are polyesters soluble in THF&DMF but not other polar aprotic solvents.


Also, what is a good general framework to be thinking about the solubilities of substances in various solvents?


