Why did Jacob and his clan not return to the Land of Israel when the famine subsided, after their stay in Egypt? We might have avoided slavery. God did not tell Abraham his descendants would be enslaved by Egypt, only that they would be enslaved. (And even if He had, surely we would not have just waited for it to happen.) Anything in the Sources?
It's like going to a dentist - you don't wanna go, you try to postpone it as you can, but once you're there - you stay until it is finished.
- It was the tradition that Egypt is the target, as Rashi explains that Avraham went down to Egypt to prepare it for the coming of his descendants and Yitzhok tried also (but was prevented).
You ask a good subquestion about the Egypt exile - why it is not hinted anywhere in the scriptures, while the other 4 as the Gm. explains the verse "תהו ובהו וחושך על פני תהום" and also "ותרדמה נפלה על אברם והנה אימה חשכה גדלה נפלת עליו" that hints to the 4 exiles: Babylon, Madday, Greece, and Rome. It worth a different question. AriZ"L explains that in length
Avrohom asked G-d to receive the Eretz Israel as an inheritance ("במה אדע כי ארשנה") instead of receiving it as a gift ("לך אתננה"), and G-d explained that the only way to do so is to go thru the Egypt exile and only then Bney Israel will enjoy the Promised Land forever.
Therefore it wouldn't help Yaakov to return to the Land of Israel, as the mission was not accomplished yet.
Also, the slavery (as with the dentist) was destined and necessary to achieve the goal of fulfilling the prophecy. Some say it might be lessened if everybody would involve in learning the Torah, but it was obligatory.
THe answer is based on the book "Beis Gnozay" by R Moshe Luriah Z"L.