Adobe Photoshop was one of the tools that helped me earn money professionally during my school and college days, so I had a nostalgic relationship with it. Then, I had a good relationship with Adobe in various ways for a long time in the 2000s.
I stopped using such tools long back, but I wanted to keep one handy to remind me of the old days. I found Serif's Affinity[1] to be a good alternative so far. I've been a customer since its beta, and I had to buy once, then an upgrade with their recent v2.0
The other good, light, quick, and easy-to-use alternative is Pixelmator Pro[2]. In the last 4-5 years, I think I have only had to pay for it twice.