Affinity Designer would be worth looking at https://affinity.serif.com/en-us/designer/

Affinity Designer and Affinity Photo are the best solutions in my opinion, especially for someone used to Adobe products. One-time payment, bundle available. Look out for discounts if it's not urgent. I got the bundle for almost half the price in January.

Pixelmator Pro is a great, much cheaper alternative but I never really got used to the interface.

https://www.photopea.com/ is basically a web based free photoshop alternative. Should do most of what you need.

The Mrs. is a professional graphic designer. Of course Adobe Illustrator is what she uses, but she recommends either Affinity Designer or Canva. I also see her using Procreate on iPad with an Apple Pencil a lot.

Edit: she’s definitely recommending Canva. It’s got a lot of templates specifically catered towards social media, and is easy to learn.

I've been using Pixelmator Pro since I've made the switch to Mac. Before that I was a long time GIMP user and so far I am quite happy with Pixelmator.

Inkscape is pretty great and multiplatform.

I personally use Krita a lot; it is a free and open source tool for creating digital art. While it's not quite as feature rich as Photoshop, it is still quite an excellent tool for designing. Check it out here: https://krita.org/en/

Canva. You’d be better off just using existing templates. Apps like Pixelmator and Affinity Designer allow designers to create art from nothing.

Https://pl32.de Is an app from a German developer, cheap and well maintained. You can do pretty much anything with it. The current version is PhotoLine 24

Second recommendation for Pixelmator Pro.

gimp

I know people hate subscription models but really nothing beats Adobe Creative Cloud, also if you’re using it for business purposes the monthly fee really isn’t anything. just be aware that you are locked into a yearly sub at a monthly rate so if you cancel before the year is up you’ll still owe the remaining amount. I think they have a bundle that is just photoshop illustrator and indesign (at least they used to).

If you’re looking for quick and easy, Canva offers a ton of templates.