The best and easiest way to buy crypto is the p2p method on exchanges, it's reliable and fast for most top exchanges and it's also safe. I believe it's the most common and we'll known method of purchasing crypto.
But now we see top exchanges like Binance, Kucoin restricting their p2p method for some reasons, making users to locate exchanges where p2p purchase method is working and also pushing other exchanges without p2p to start up such purchase method
I agree that using centralized exchanges to buy or sell bitcoin is the easiest way but not the best, the best to me would be a platform without actual asking for KYC but most of the exchanges today do ask for KYC which many people find not attractive. But in terms of ease the centralized exchanges are a place to go to, they have higher liquidity than decentralized exchanges and they are more user friendly than them also.
As for the restrictions on this exchanges it bows down to the individuals country. There are countries now that this exchanges have regularization problems with and they needed to restrict the countries citizens to avoid sanctions. Although you can still perform other actions there too.
^ I agree with your sentiment, my two friends frequently use binance p2p since long time and they have had good experience so far, no scam till date.
The thing is you hardly get scammed on centralized exchanges like this except you are naive yourself, once you don’t release your funds except you have confirmed payment then you’re good to go