300 dpi versus 72 is a real difference when ink hits paper, so that part of the fix makes sense. The color profile matters too, since a print shop or gallery is working in a different space than your screen. But the "screenshot" comment usually is not about dots per inch at all. It is about the image having no surface, no tooth, nothing for light to catch. A gallery owner in Savannah is looking at work under track lighting and comparing it to oils and pastels hanging nearby, where texture is the whole point. Adding grain helps, but a single texture layer over the top can read as a filter if the brush strokes underneath are still too clean. What fixed it for me was building the grain into the layers as I painted, so the marks had some tooth from the start.

My dad told me a story about a guy he worked with in Twin Falls who did the same thing, packed brackets every 8 inches thinking it would hold more weight. The wood just flexed between each one and made it worse, kind of like how too many nails can split a board. So yeah, the chart on the back is usually right.