Quality is only objective if you only use objective metrics to measure it like the number of bugs, stable framerates, polished graphics and textures, good resolution, good controls and camera, good sound editing, good physics, good voice acting, quality of life additions, etc. There is an overall agreement and common sense about those. I've never met anybody saying that likes to play a game with unstable framerates or clunky controls, so I see those metric as objective
But when evaluating arts we also include subjective metrics: What makes a OST good, what make art direction good, what makes a story well written, what makes a good design character, what is good level and world design, what even a good gameplay supposed to be? Those as more subjective criteria, there is no proper answer for any of that
That's make quality of games indeed subjective
