You are certainly right that Kagan and Sotomayor are not moderates. And whether they are good or bad justices is an issue on which reasonable minds can vary. But suggesting that they had anything less than impeccable qualifications is unfair.
Sotomayor had a very traditional SCOTUS resume: Yale Law, 4 years as DA, 9 years in private practice + various political jobs, 6 years as USDC judge and 11 years as USCA judge. A strong case can be made for her as the most qualified of the current 8 justices. The other 3 worthy of consideration -- Ginsburg, Breyer, and Alito -- each served for a decade or more on the USCA, but none had USDC experience as well.
Kagan had no prior judicial experience, but she had an incredible resume nonetheless: Harvard Law, USCA and SCOTUS clerkships, 4 years as a law professor, 4 years in the White House, 4 more years as a law professor, 6 years as Harvard Law School dean, and 1.5 years as solicitor general. Some argue that her lack of judicial experience made her under-qualified, but prior judicial experience has never been a prerequisite for SCOTUS. Scanning down the list of justices who never wore a lower-court robe (roughly 1/3 of all justices), the following names catch my eye -- Rehnquist, Powell, Warren, Douglas, Frankfurter, Brandeis, Chase, Taney, Story, Marshall, Jay.