Recently it's reported that Bitcoin Core will disable BIP70 support by default in the next major release (0.19.0): https://cointelegraph.com/news/sorry-bitpay-new-bitcoin-upgrade-proposal-disables-bip70-by-default
I heard that BIP70 was controversy, especially when BitPay started to force their users to pay through BIP70 since 1 year ago or so, instead of showing the bitcoin address directly to the user.
What's the problem BIP70 was supposed to solve? Does BIP70 actually provide any advantage or disadvantage? Why did so many people oppose it?