These are two different things entirely which should not be compared.

If you like being on social media, there is nothing bad about staying there if you have time for it, but the difference is that doomscrolling or what you call it is not involving money, but make sure social media does not affect your sleeping time.

Gambling is also good if you do it in the right way. Social media supposed not to affect someone's gambling activities. Some people Neill like social media and also like gambling.