but what I'm surprised now is that many people don't realized this and even insisted on the argument that BNB is better than ETH in terms of transaction fees.

As you said before the gas price will continue to rise because price itself for example ETH or BNB was rising, Yes you're right about fee will high because it's pegged to the price while current BNB Fee for example was around $0.4 and this will continue to grow over time but the main problem here BNB, Polygon or any other PoS Coin will always have flat fee while Ethereum Fee was really fluctuate, From 1 Gwei jumped to 600 Gwei so the gas fee was doubled or even tripled even more not only from price movement but also the network itself.