Is TAing a necessary evil?
It may be necessary; some universities require students to TA even if they have other sources of funding.  It need not be evil.  It depends on your attitude (do you want to help students learn?) and which faculty you are working with (Do they care if you help students?   Do they care if you learn something yourself?).  Unfortunately you usually do not get to chose who you work with.  TAs (and also faculty) should receive training in how to teach, but may not.

There are many other ways to fund education, some of which pay better than being a TA, and some of which are more prestigious.  They all have limited supply.