Modifying attribute using operations

Hi 👋 
So what i'm trying to do is, as said in the title, edit a player's attribute (here generic.max_health (I am on 1.21, not above 1.21.2)). I tried using modifiers, but thes can only be used once by entity, and i want to be able to re-do the same operation as much time as I want. What I am trying to do now is to do the operation in a scoreboard, then insert it into the player's nbt. To do so, I tried running execute store result entity @s attributes[{id:"minecraft:generic.max_health"}].base double 1 run scoreboard players get @s test (where test is my scoreboard), but right now, my heart amount doesn't change, and its just returning my current score value (I'm used to trying stuff i'm not really comfortable with in-game before putting it into a datapack). Does anybody know what I'm missing ? I know it's a long message, but I would really appreciate me if anyone could tell me what's going on ! Thanks by advance !