Agreed, with one caveat.
Any program will do, as long as it has layers, but you need to know how to do what you want in that program. If you're self-taught and are an expert, then no worries. If you're still learning, then choosing a more obscure program (even if it has layers) means that folks might not be able to help you find tools, or point you to settings, options, or what-not, that you ask about.
We can only help with what we've used, is my point. the big 3 are Photoshop, Paintshop Pro, and Gimp. By that I mean those are the most common programs and the ones that will have a large pool of help in this forum, if you have to ask any questions.