When Black Clover first came out there was a lot of controversy to this matter. But my opinion after watching all the episodes that are out as of now, I know this is no a Ripoff of Naruto. Here is my reasoning why.
Black Clover Synopsis:
Asta and Yuno were abandoned at the same church on the same day. Raised together as children, they came to know of the “Wizard King”—a title given to the strongest mage in the kingdom—and promised that they would compete against each other for the position of the next Wizard King. However, as they grew up, the stark difference between them became evident. While Yuno is able to wield magic with amazing power and control, Asta cannot use magic at all and desperately tries to awaken his powers by training physically.
When they reach the age of 15, Yuno is bestowed a spectacular Grimoire with a four-leaf clover, while Asta receives nothing. However, soon after, Yuno is attacked by a person named Lebuty, whose main purpose is to obtain Yuno’s Grimoire. Asta tries to fight Lebuty, but he is outmatched. Though without hope and on the brink of defeat, he finds the strength to continue when he hears Yuno’s voice. Unleashing his inner emotions in a rage, Asta receives a five-leaf clover Grimoire, a “Black Clover” giving him enough power to defeat Lebuty. A few days later, the two friends head out into the world, both seeking the same goal—to become the Wizard King!
Just by reading the Synopsis I understand why you might think this is a Ripoff of Naruto, but let me explain. Black Clover happened to be one of the series to start airing not too long after Naruto ended (Naruto ending March 2017 and Black Clover starting October 2017) So with Naruto ending and this series starting up, Naruto fans would have still been in the Naruto mindset and would have been just looking to compare the differences and the things that are alike with the 2 series. I know this because I have experienced it. Me as a Naruto fan all I did The first couple episodes of Black Clover was compare and find things that were alike with the series, but if you stop looking at just the surface of Black Clover you’ll see how different these 2 series really are.
But back to the point of people comparing series. Makoto Shinkai the creator of Kimi No Na Wa (Your Name) said himself that he hated how popular Kimi No Na Wa has gotten and is now afraid to make other films. he said this because when one really good series is made and it finally ends, when another good series come out afterwards, all the people will do is compare the first popular series to the newer series that comes after because of how popular and good the first project was.
So because Naruto had come out first, was very popular and had a large fan base when a series like Black Clover had started all these fans not being able to watch Naruto anymore seeing it ended, they started watching Black Clover and their the first instinct as a Naruto fan was to compare Black Clover to the series they loved. (Naruto)
One other thing people need to understand is that both Naruto and Black Clover are Shonen series. So when people say “Wow… Asta wants to be the wizard king, that’s a ripoff of Naruto wanting to become Hokage” and to that, I say NO it’s not a ripoff because…
One of the biggest shonen anime tropes is the underdog wanting to become the best at what they do/become the leader. (which can go for both Naruto and Asta) So if that was the case then Naruto would be a ripoff of Hunter X Hunter seeing the anime came out 4 years before Naruto and Hunter X Hunter is also an underdog striving to be the best type of series.
So by say that Black Clover is a ripoff, then Naruto would also be a ripoff of:
Ninku (aired 1995)
Flame of Recca (aired 1997)
AND MANY OTHER SERIES!
So I hope you have now changed your mindset on Black Clover and if you have not started watching it then I really recommend you do, it is an excellent series!