Arguing which football player or TV show is better is very different and a higher level of discussion
Yes there is worse, nickelback is just 'different' to Black Sabbath right?
Music isn't a competition, Football is. Yes, Nickeback is just different to Sabbath. They don't pretend to be what they're not, they're a popish teen rock band for easy listening kids/radio to dig in. There's no reason to compare two different bands not only from different decades/societies but that offer and bring to the table the completely opposite. That's childish, really.
The easy way

yes just rip off a few blues songs and then in 5 years time you will write Kashmir and Achilles Last Stand
What is this even supposed to mean? What ripping off songs early in their career has to do with developing writing skills later on? I'll repeat if you didn't read the first time, covering other artists was a common thing in the 60's, what Zeppelin did wrong was not give credits to the actual composers. Which later on was resolved, when they were brought to justice.
If you've ever listened to any of the so called 'rip offs' most of them are very different to the Zeppelin song... In case you haven't realised music doesn't come out of a vacuum.
classic pure blues ripoff this is
Just to make a note; i've been a Zeppelin listener for almost 3 decades and yes, i've heard all of their "rip offs". They're not a "few", they're several from several artists. Some sound exactly the same, some they were disguised with subtle melody changes, others only the lyrics were taken, etc...