It's way too easy to criticise those who are considered legends. Most people who hate them seem to be contrarians. And as to the whole plagiarism skiffle, that's just a load of horseshit. Everyone in the industry was rewriting and covering each others songs back then.
"Babe I'm Gonna Leave You" This shares similar lyrics but page completely changed the song and turned it into a flamenco rock song.
"Black Mountain Side" You have to be totally fucking naive to credit that to Bert Jansch's Blackwaterside since the song itself is a traditional piece.
"Bring it on home" Yes this is a straight cover, but in between it is an original turn on the song.
"Communication Breakdown" If you want to criticise that for being stolen at least be right. It sounds more like Livin Loving maid (which was a filler song written for the album)
"Dazed and Confused" Yes that is very shady to do a cover like that but he did make it his own, it wasn't a carbon copy. Also why shouldn't the Yardbirds get any flak as well? They played it too and as far as I'm aware they didn't credit Holmes.
"Hat's off to Roy Harper" yeah. yep, not really arguing with that one.
"How Many More Times" Again, I keep repeating myself but yada yada made it their own song by rewriting.... not a carbon copy.
"In My Time of Dying" another traditional piece that Bob Dylan didn't even write. Their two versions are completely different (and I love them both)
"Since I've Been Loving you" Yeah ok that seems seedy.
"Stairway to Heaven" From a music writing perspective, Taurus were being a bunch of losers. A chromatic chord progression is very common, Taurus weren't the first to use it and they aren't the last.
"White Summer" Yeah most definitely a case of Page trying to be sneaky.
"Whole Lotta Love" These share lyrics, and not the famous riff that Zeppelin wrote, of which the song is known for.
So take what you want from what I said, but just know that I'm a big LZ fan so I'm very biased ;)