Yes. What you’re seeing is the printed halftone screen from the CMYK offset process, not simply a color-mode problem. Converting the file to RGB alone will not remove the visible dots.

To reduce the pattern, you need to descreen the scan. Two approaches mentioned are:

• FFT/frequency-domain descreening: This can work very well for removing regular screen patterns. Tools such as G’MIC for GIMP provide FFT-based functions.
• Blur + sharpen: Apply a small Gaussian blur until the halftone pattern becomes less visible, then use unsharp masking to restore some perceived detail.

There is usually a tradeoff: removing the screen pattern also removes some real detail, so the goal is to find the best balance.

After descreening, you can convert the image to RGB if needed for normal editing or display, but the key step is descreening first.