I read about tissue fluid in my book. It says that tissue fluid assists in delivery of nutrients and removal of waste products. I googled about the function of TF and found this pretty much everywhere.
" Role of interstitial fluid
Interstitial fluid acts as a kind of fuelling station in terms of nutrients for our cells. Interstitial fluid contains glucose, salt, fatty acids and minerals such as calcium, magnesium and potassium.
The nutrients in interstitial fluid come from blood capillaries. Interstitial fluid can also hold waste products which result from metabolism."
My question - can't a normal circulatory system do the same (deliver nutrient and take away waste) as efficiently as with the tissue fluid? Of course not, but why not?
Probably tissue fluid gives more surface area for diffusion to and from cell. But we know the adaptations of capillary. Should not that be as good as tissue fluid?

Why not? For one, the circulatory system does not make you sweat. Every cell needs to remove waste and receive nutrients. The circulatory system is encapsulated, for lack of a better word. Blood is contained within arteries, veins, and capillaries, etc. It is not free flowing