The thing is:
stuff are more effective when played as "meta".
Example: ADC Ahri works just fine, but she is more effective. So, her "meta" build is APC
Example: Ahri is a fine mid laner, she has some wave clear, roaming potential and pick potential, all good. But she isn't as strong as current meta champions that are more suited to fight the champions the enemy picks (or are overpowered). That's why some people favor picking meta over comfort.
HOWEVER, learning a champion takes time. Picking "meta" just because is "meta" while you didn't put in the time to learn it (like most players don't actually put in the time at the start), you will harm your chances by picking meta over comfort.
Personally, I prefer mechanically easy champions. So, even when Azir was meta, my mid lane picks were (pre rework Malzahar, Morgana, Ahri, Diana).
Also, since it takes time to learn a champion. You might want to use that time to master your comfort champions that suits your playstyle.
Even in a fight between a Sword user, Spear user, Scythe user, Knuckle user, Mace user, Axe user.
Even if right now most people are using swords -> which means spear wins (coz its longer) and it makes spear meta. If you got good enough with your preferred choice, you are going to kick the "ass of the meta weapon user".
Even if they know to use all from above, if you are better on your own, you can win :)
Then there are "Gun user", "Riffle user", "Nuke user". Those are OP or cheats ;)
PS: this worlds we had a demonstration that meta doesn't really matter even in the highest tiers. You can play off meta (brand support, mf support, zac jungle, etc) and win even in a game between the best 50 or so players in the world.