And the actively managed mutual funds that have consistently outperformed over a 10 year or longer period are fairly easy to find with some work.
Sure, but finding them tells you nothing about their future performance. Follow me through the following thought experiment:
Assume that mutual funds do not outperform index funds, but just give market returns on average (before fees). Let us therefore assume that 50% overperform and 50% underperform every year. Think of these funds as being managed by monkeys buying and selling stocks literally randomly.
Mutual fund companies offer many different funds. If you start with 1000 funds 10 years ago, then on average one of them will have (randomly!) outperformed over 10 years straight,
every year! (Because 1/2^10 = 1/1024.) This fund will be in the news, investors will flock to this fund hoping for outperformance. But the fund is still lead by a monkey who buys and sells randomly, so its future returns are
still only market average - and below average if you have to pay a management fee to the monkey. It is just survivorship bias: people look at this one fund and think "10 years of consistent success, there must be a superior strategy behind this", ignoring the 500 funds that had a 10-year underperformance before fees, because those funds are eventually closed and forgotten.
Empirical studies show that (correcting for risk, i.e. choice of asset class) the performance of mutual funds is generally very close to that of monkeys buying and selling randomly. If you correct for fees, it is worse. That's why it does not make sense to select funds by past performance: you are probably just choosing the luckiest monkey, and his future returns are just as random as that of all the other monkeys in the game.