I agree I the point it’s impossible the way you mentioned but there is a but - you are referring to a brute force attack - which means you try to find the key by trying all possible keys
secondly the article you are referring compares computers based on FLOPs which means floating point operations per second which is the most useless way of targeting the problem
AES does not have floating pints in the calculation ist pure byte operation
while a floating point operation reserves an amount of bytes after the comma - which in this case is a waste of processing power. a specialized ALU (arithmetic logic unit - which probably have heard of in while reading of GPU ) has a large advantage on crytptography as it shift bytes parallel without having to spare space after the comma
nevertheless to say that an ISP or state internet surveillance unit does not go on brute force.
a hacker sniffing your network might have to, as he cannot record the whole conversation between a vpn server and your client
And even he could, he would need more calculation power than he possible can carry, to just decrypt the every single time changing handshake encryption of your vpn
and exactly there is the catch
the two vpn partner need to handshake and confirm the way the will encrypt in future, which implies they will exchange part of the keys to be on the same page
while the hacker will not have all required communication between two endpoint stored from a single catch, the ISP will, which tremendously reduces the effort of finding the encryption keys along the vpn
an ISP can store every single bit and byte a long way back which likely will allow him to catch the essentials to decrypt your Pakets in the long run. Usually you download a file from a vpn provider which gives you a certificate and other key information to uncover the protocol information during the handshake - this is the first piece of the puzzle.
the question is only is it worth to get the information of the individual
just a little one on the side if AES is impossible to hack the NSA would have given up a long time ago - but they didn’t and the reason is simple, they are able to collect all the bits an pieces to finally decrypt your data pack
but you are right in the point for you and me it is impossible because of the calculation power required to start a Brute force attack