I don't like grouping stages and playoffs together. 2 different things. 1 is 15 years old.
And of course not everyone will agree on everything, but I'll defend stages and current point system here:
They've acted as checkpoints to gauge entire race performance, and reflect that in the most accurate point system NASCAR has created imo. That addition, has allowed the playoffs to be less gimmicky until Homestead. The points advantage that carries over from the regular season makes it very tough to be ousted, before that point, depending on how dominating your season performance has been. In past playoff years, the regular season carry over was not enough, now it is rewarding.
Improved other aspects, Qualifying for stage 1 checkpoint, would still like to them add more reward for Pole position in the points imo.
The days of hanging back, go to work on your car all race long, and show up at the end are gone. Unless you're foregoing stage points as part of your race strategy for the win. Of course you can opt to do that, if that's how you want to run it, or your car requires that type of transformation to have a chance. It has introduced more strategy options into the race. I personally don't mind the stage end yellows, since we're seeing plenty of green flag run in all stages, especially stage 3.
I will venture a guess that you long lost interest before the addition of stages. I don't quite share your level of distaste for the playoffs exisitng, but I would prefer if they ran this point system without a playoff. I understand why they want it (guarantee Homestead, late season drama, talking points etc), not that that's a good thing. I'm just not a believer in 1 race deciding what is supposed to be a year long achievement imo.
For race day experience enjoyment at the track, I don't see how that worsens at all with either of those. If anything, I would lean on them being more of a positive for that. As for on track racing aspect, I would say both of those force the driver's to push harder for longer and put their nose into spots where they wouldn't have otherwise, if they could sit back and point race carefully.