There are several areas of the game where players claim the designers seem to merely coast on the collective wisdom of us gamers, than actually making sure the respective "truth" is actually true.
Disclaimer: Do note that in games that aren't actually challenging, none of this matters. So if you aren't playing in a campaign where the difficulty actually rewards optimal builds, this thread isn't for you.
Here are a few examples, and you can fill in with your own.
---
TRUE: 5E does not have the concept of fast or slow builds, except maybe someone in heavy armour without the required strength.
TRUE: 5E rewards melee builds when you are in melee.
For Rogues this is doubly true. The game does not provide a single compelling reason why you shouldn't risk a little damage to use two weapon fighting in close combat when all your abilities get a second chance to trigger compared to being in range.
Taken together, it isn't even funny how much better a melee character is than a character in melee.
FALSE: Please. Without feats, melee is just as good. Cover, lack of Opportunity Attacks, and conditions like Prone only benefit melee. So the party is much better off staying in melee and never actually allowing the monsters to get away, punishing them if they try.
(That's actually true with feats as well, but I digress)
TRUE: Maybe even false if the conditions are reversed. Alert, Mobile, Crossbow Expert and more all help the Rogue as much as other feats help others/
(Don't worry, I'm not going to put something insulting and dismissive here, that'd be stupid unless I was trying to start a fight.)
TRUE: In fact, the only other class that compares is the land druid, or a warlock with an above average number of short rests. The reason why is Arcane Recovery. Even if the Sorcerer used all their Sorcery Points to create spell slots, they still can't make as many high level spell slots as Arcane Recovery refreshes, excepting 1st level spells.
Disclaimer: Do note that in games that aren't actually challenging, none of this matters. So if you aren't playing in a campaign where the difficulty actually rewards optimal builds, this thread isn't for you.
Here are a few examples, and you can fill in with your own.

---
"When you play a martial, choosing a slow build is just as viable."
TRUE: 5E does not have the concept of fast or slow builds, except maybe someone in heavy armour without the required strength.
"Choosing a melee build is more viable than being in melee."
TRUE: 5E rewards melee builds when you are in melee.
For Rogues this is doubly true. The game does not provide a single compelling reason why you shouldn't risk a little damage to use two weapon fighting in close combat when all your abilities get a second chance to trigger compared to being in range.
Taken together, it isn't even funny how much better a melee character is than a character in melee.
"Choosing a melee build is just as viable without feats as with them."
FALSE: Please. Without feats, melee is just as good. Cover, lack of Opportunity Attacks, and conditions like Prone only benefit melee. So the party is much better off staying in melee and never actually allowing the monsters to get away, punishing them if they try.
(That's actually true with feats as well, but I digress)
"Choosing to play a Rogue is just as viable with feats as without them."
TRUE: Maybe even false if the conditions are reversed. Alert, Mobile, Crossbow Expert and more all help the Rogue as much as other feats help others/
(Don't worry, I'm not going to put something insulting and dismissive here, that'd be stupid unless I was trying to start a fight.)
"Choosing the wizard class is the best choice for casting a lot of spells."
TRUE: In fact, the only other class that compares is the land druid, or a warlock with an above average number of short rests. The reason why is Arcane Recovery. Even if the Sorcerer used all their Sorcery Points to create spell slots, they still can't make as many high level spell slots as Arcane Recovery refreshes, excepting 1st level spells.