People debate this concept all the time, especially given the acknowledgement in Gen 7 that maybe you need to be willing to use strong Pokemon in order to do well.
But someone recently posed a counter-argument I hadn’t considered before: what if using weak Pokemon is a necessary step in becoming a strong TRAINER?
What if, in order to understand the battle mechanics better, you need to put yourself in scenarios using weaker Pokemon in order to understand battle mechanics which usually become irrelevant in higher tiers of play?
What if the first players who figured out that building their team around Landorus and Heatran only arrived at that conclusion by first figuring out how to optimize a Sunkern-based team in a babby cup?
What if the players who try a little of everything are better able to expect the unexpected?

I am not a competitive player. I am building my first battle teams based on cursory notes from what I’ve learned on /vp/ and what I’ve gleaned with summaries of previously-tested battle sets. If these resources weren’t available, all I would have to go on are my own trial and error.
I am curious what other anons think about this piece of the great debate about competition-level Pokemon. Do you limit yourself to the already tried and tested successful sets/teams, or do you explore weird setups and create new sets? Do you get your shit packed in by a Pachirisu with a sitrus berry, or do you have a rough backup plan for taking down a Sturdy Lv 5 Aron with leftovers, sandstorm, and endeavor?