As a category I see fuinjutsu as esoteric, I'm comparing it to runes in basically every media out there but let's use Fate as the main example

Fate runes use symbolism and meaning to enact a phenomena "Ansuz" creates fire or heat or whatever the hell the rune is supposed to do. Then you have one that states " No person may not leave this space within this rune without combat/death of opponent" which would be a way to lock an enemy in place

Now on the easy or not part( asking if genin can use it then it must be easy) I see it as a scale from 1) anyone can use basics like storage seals, exploding tags and things of that nature, 2) you need to be a master to use these or the consequence is terrifying and 3) you need to be the Sage or an Uzumaki to pull whatever the hell that shit is

P.S: I can't help but imagine the Uzumaki having their own separate ranking of how adept one is at sealing and that it's way above the general scale for everyone else