Aesthetics

Taking Aesthetics for improving culture and get social policies more quickly without having to wait so much for choosing the next policy it's a good strategy, or should I take only if I wanna go for a cultural victory? Help me please.

I've always gone with the second option. I never use Aesthetics unless I am going for a cultural victory.

Sometimes if you are doing a hybrid CV/DOM game and using autocracy I put 1 point in it and then never go back again.

If you are not after culture i would rather skip it, since hardly ever you have no other options. Since policy cost is rising, then every policy you take increase the cost of future ones without real benefit. So For example Ethis is more holding you back than helping.
If you have spare SP then always better options are:
Patronage and Consulates and mass pledge to protect will grant you a lot of random bonis and some of them will be useful.
Rationalism is generally good (Secularism and Free Thoughs).
If you are aiming for Autocracy or Order then Commerce + Mercantism could save a lot of gold (and still give some science) when you mix it with BB and Skyscrapers or Mobilizacion.
If start with liberty dipping early into Tradicion and Aristocracy could pay off. This border growth helps a lot.

So generally before ideology you will have enought to choose from.

If you are after a Cultural victory, the tree is useful, but not as much as Rationalism.
But you could open Aesthetics tree & then switch to Rationalism as soon as that's available and then complete the tree after Rationalism finishes for the doubling theme bonus.
If doing this, you'd also want to open Exploration early enough just for the Louvre (but wouldn't dip any further)

If not intending a Cultural victory, this tree can cause an accidental Cultural victory.

This tree is especially good for Poland. Poland actually has time to complete a full two trees before Rean era (and use their free policy on opening Rationalism that turn)