The system is not new, as far as I know, an approval system is also used in games like Dragon Age.
In Dragon Age 2 it was not just approval system and it worked with both: companions would leave you at certain moments and you could romance them while practically never being agree with each other. Larian would need to create "flirt" level in addition to approval level to implement that.
I don't like it. They returned the usual approval system to DAI, because there was more logic in it.
PoE2 have a "reputation", but as far as I know, it is more difficult to understand what companions approve, but still, you must act in a certain way to please them. Conditionally, there is an approval system in many games with romance. The most fun approval system in Tyranny, there are no romance, you can become good friends, but if this does not happen, then you inspire fear for them.
The approval system is good because you understand how you need to act. Although sometimes it's not enough to get a happy ending (damn you Aloth!)
edit: I also want to add something. In DA2, you really need a approval, it just works BAD. I know this because I thought that everything depends on flirting and personal quests, and with this I did not get a Fenris romance. Because my approval was average. In DA2, you must either have an 80+ disapproval or an 80+approval. It's called a love or hate romance, but you still need to play a certain way. It's just that you are also given the opportunity to build a romance by playing against a character, but not alternating your options.