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.