I get you. Its both really.
It's poignant because it harkens to simpler times and game worth is often not objectively related to its quality, but rather the feelings it used to elicit, the feelings it brings back.
It's poisonous because it will always set our expectations to a level that is unattainable because we aren't trying to replay the games, we are trying to re-feel those feelings, be innocent and curious again.
Now, that doesn't mean old games don't have objective qualities, they do. And it also doesn't mean modern devs can't be lazy, they absolutely can.
This perception stems from the ease of development nowadays compared to then, because in the past solutions were bespoke and computing resources were limited; limitation is inspiration, as it were.
On the other hand, the industry shifted massively nowadays and budgets as well as expectations balloon out of control. Are there hard working modern developers and studios? certainly, but a lot of the industry isn't trying too hard.
So yes, nostalgia is a bit of a poison, but one that can be somewhat reveled upon.