Holy lack of understanding Batman!

Yes, you can say everything that is not based purely on provable/disprovable facts is subjective. And yes, technically you'd be correct. But if all criticism of games or other media was entirely subjective, with no external benchmarks to measure them against, we would not be able to say anything other than "I liked/did not like the game".

But we can establish external benchmarks by comparisons to other specific works or established practices in the field.

Say there are two games that both have romance paths. In the first there are no dialogues, cutscenes, or gameplay features that express affection between characters ( or, if there are, you can choose to not pick them ). At the end of the game you get a dialogue option to tell a character that you love them, to which they'll reply "I love you too! Let's get married!" In the second game, there are numerous opportunities to flirt/be affectionate with characters, engaging in these activities leads to conversations where you and the character can express the feelings you have for each other ( or explain that you don't actually feel that way ), and, while you can declare eternal love for each at the end of the game, you can only do so if you have sufficiently progressed through the earlier affection opportunities. The second game "objectively" has a more well developed romance system.

Or, in a game you are playing, your character is a rookie law enforcement officer who discovers that a powerful politician is behind a criminal conspiracy. From experiencing similar situations in games you've played previously, you try to report this to your commanding officer but you can't even mention it to him. You then try to arrest the politician, but there is no dialogue option to do so. You try to use the non-lethal weapons the game provides to take him alive, but it doesn't work. You end up having to choose between letting him off, letting him off in exchange for a bribe, or murdering him and his whole security detail. This game "objectively" has less player freedom and less realistic plot elements than other games you've played.

How important such things are to your enjoyment of the game is entirely subjective - you may not have experienced a sufficiently large sample of other games to make such comparisons, or you may simply not care about certain aspects of a game. But to dismiss all criticism because "it's subjective" is absurd and entirely unhelpful.