is it healthy to engage in these two activities excessively?
Whether it's healthy or not actually depends on how the individual engages in either of them, however, if there's anyone which can be said to be dangerous engaging in it excessively it should be gambling because if we're to count the damages that unhealthy gambling habits has done to indiscipline gamblers it grossly outweighs those of doomscrolling or whatever name you all call it.
You're right, maybe all of us in other ways might have been found doomscrolling at unaware all the time we must have been surfing the internet browsing, while when it comes to gambling, we have to understand what it is made up of, we cant be gambling in an irregular pattern and also expect not to get addicted or totally wrong about it, this can easily get us addicted if we are not been careful and take the way we surf the internet together to how we are gambling, it could be a more worse condition in gambling.