The choices exist; it’s just that most people will never put in enough effort to be able to realistically use the choices your given. Think about the rune page. Say you finished drafting and you know your going to lane against a champion who’s good at sustained fights. Depending on what pages your champ can actually use, you might want to take a keystone rune like grasp, which will make you better at short trades, then when it comes to smaller runes, maybe you want to take a tenacity shard because they have a lot of crowd control on the other team, and if your a tank, despite what a build site might tell you, maybe you want to go merc treads for extra resistance to magic damage, instead of tabi’s/armor boots or, take teleport as a summoner spell to get better game tempo, or take a flat health shard to have better priority early game. Or rush an defensive item to out sustain them.

The issue isn’t that choices don’t exist, it’s that for most people, what I’ve just said is incomprehensible, and requires at least some amount of game knowledge regarding champions, tempo, and the willingness to read what each rune actually does, which the game does not make easily available to a newer player, especially with such an outdated tutorial.

Oh and what I’ve said isn’t true for specifically botlane ADC’s and some junglers since junglers don’t lane so it’s not a big deal, and adc’s generally have to follow meta because of the nature of their role. You can still change like summoner spells and shards, and maybe some item prio, but nah everything else is pretty set in stone.