What risks are S&P 500 investors being exposed to as a result of the S&P500 rule change related to the SpaceX IPO and the IPO itself?

Some time ago some of the finance YouTube channels I watch were talking about a proposed S&P 500 rule change that would add SpaceX to the fund right after its IPO, and other investment advice channels were talking about how it's a bad idea to buy stock in a company right after the IPO because that's the time the shares are going to be as overinflated as they're going to get. And of course, this was all a couple months ago so new information is out and the situation might have changed.

Can someone provide some clarity on the likely combined impact/outcomes of these 2 events and maybe some risk mitigation strategies?

Are newly IPO-ed stocks really that bad? What's the status of the S&P500 decision now? What are the questions I should be asking here, and the answers to those questions?