Problem with majorify of those "decentralized exchanges" is that they are not really decentralized. Good example of that is Pancakeswap that is based on highly centrazlied BSC so how decentrazlied it can be in the end? In the same time, truly decentralized Bisq has only ~$100k daily volume so it makes it very costly to buy/sell any bigger amount of bitcoin.
You can not exchange more than the main coin and its tokens. Just like BNB and BUSD, they are very centralized and owned by Binance, their decentralized exchange is not completely decentralized.
Untrue, on pancakeswap you can exchange any token to any token. Bnb chain may be centralized but nonetheless pancakeswap uses smart contracts to make a trade without handling custody of your funds to anybody, which makes it dex.