I’m seeking solid, fact-based arguments to explain why Bitcoin remains the superior option and why altcoins often fail as alternatives.
You won't see much facts to back your argument because while most altcoins are shit, crypto doesn't always have to be a zero-sum game. That is, the statement: "if it's not bitcoin, then it's 99% a scam." is not true
Most of these altcoins have changed people's life just as bitcoin did and they would continue to do so whether you agree with them or not.
However, what makes a lot of sense (and I've seen a lot of bitcoin Maximalists do) is to recommend keeping a bitcoin portfolio alongside an altcoin one but Bitcoin has to be the #1 asset and have the most weight.