HD did quit selling it. They were required to by law. However, the stuff they sell is still green and it is treated now with something else.
You can paint it. You should paint it. But you should let it sit for
6 months to a year to dry out first. These boards are pressure treated and dipped when they are right off the tree. If you deck is new you will be stunned at how much the boards willl shrink not only across the face but sometimes end to end. I no longer build decks, and the reason is that the material we buy is so poor that I wind up with a lot of warranty work. I don't like the product and neither do my clients after a couple of years.
But if I built a deck for myself, I would probably do one of two things: try to find some kiln dried pressure treated and/or use synthetic decking for the walking surface with wood for rails, steps, etc. But kiln dried treated is hard to find and is usually quite expensive. And the cost of synthetic material is so much it is scary.
OR, I would think about building an all wood deck with yellow pine as a deck surface and treated for the rails, steps, etc. I have seen many an old fashioned porch here in the south that have been made from yellow pine that has been religiously painted and they are in great shape after many decades. Be aware that you paint the YP only after it has been down for a month or so, then prime it with a thinned coat of deck paint. Then finish off with two coats of oil based exterior deck paint and you should be good for a few years. You will need to renew/recoat the walking surface, but the oil based deck paints are surprising durable. Besides, you can roll out a deck in no time with a
4' extension.
Just my opinon. Others will certainly have theirs.
Robert