My first thought is that the intonation is off. the bridge saddle needs to be set properly.

Height of the strings also matter. As you press down, you are stretching the sting and that affects the tuning. But the proper intonation settings are extremely critical.

If you're not sure how to do a proper set up on the guitar, take it to a luthier and pay them to do the set up for you.

I've also seen people complain about their tuning and it ended up being how they applied the pressure from their fingers. Our guitarist in one band had a Strat and was always complaining about his tuning. He loved that my SG always kept perfect tune. So one night, we swapped for a set. Suddenly, my SG was all out of tune and the Strat kept perfect tune. It came down to the person playing the guitar since both guitars were perfectly set up.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.