To be fair, high-scoring a work just because you like it is very irresponsible. This is a nice manga, a good one, but it is nowhere near even being an 8/10. If you score it like this, then how would you score things like Berserk, Monster, Otoyomegatari, GTO, on and on? 20/10? 15? You have to be responsible with those scores, other people use them as a guidance.
If your scoring system is only based on comparison, not purely on the value of each piece... I don't think you are someone to talk about scoring anything.
You must deduct points for each problem in each work, not because another piece is a grand epic, a magnificent drama, a fun and ever changing analysis of different characters, personalities, their weaknesses and how to improve of many kinds of people.
Yes those pieces are a 10/10 for those an other reasons, but the people that give this a 10/10 recognize thos work as the best romcom due to its organical development, the point of view, the best ever use of chunni as in the reasons behind every part of this behavior, the edginess and cringe intensionally used, the subtlety of Yamada noticing that Ichi wants to grow and to be better so she is always helping him to move forward, other things that this Manga does to deserve a top spot.
If you have opinions or your own reasons to give this a 8/10, it should never be because you idolize certain works and it hurts you when they are touched by something that comes from BokuYaba's genres.
TL;DR: At least score what you are currently reading, not in comparison, but based on what you've learn about literature analysis and critique.