While I can’t honestly refute this in its entirety, I think it’s relevant to point out that only one group/artist can be “first” in a genre. By that argument you’d really have to write off everybody who wasn’t “first”.
“Led Zeppelin copyists”: Remember the guys in Rush were 18-19 years old when they recorded their first album. Of course they were heavily influenced by the music that was popular when they were teenagers. And unlike Zeppelin (a group of musicians who had been working professionally since the late '50s/early ‘60s), their first album was all original material, not reworkings of earlier artists’ material.
Neil Peart replaced John Rutsey on drums in 1974, in time for the band’s first tour. Having spent some time working the music scene in England, Neil suggested trying the prog rock idea. And it worked for them. Inspired by the likes of Yes and Genesis? Sure. But they sound nothing like either of those bands - they developed their own unique style. And I look at musicians of the '90s who list their influences, and I hear Rush mentioned far more often than Yes or Genesis. While I’m not a famous musician, I’m the same way. Hearing Geddy Lee play was my entire inspiration to become a bass player. Yes/Chris Squire has never inspired me to do anything beyond trying to learn Roundabout and Owner of a Lonely Heart, and I have found most of the pre-Abacab Genesis I’ve heard to be unlistenable. But I’ve been compelled, since I first heard them in 1980, to try to learn to play every single Rush song. I still haven’t succeeded, but I keep trying.
The Police? They weren’t the first to incorporate reggae into rock. They just did it better than anybody before them, largely because they were honestly better musicians. Rush did it in 1980, albeit as a poke at the critics who were at that time gushing over rock bands who incorporated reggae.
All those grunge bands that Rush “copied” in the '90s? As mentioned above, half of those grunge musicians in the '90s cite Rush as a huge influence/inspiration. So we have a recursive argument here. Which reminds me of an interview I heard on the radio one day with John Stewart, original member of the Kingston Trio (hugely popular folk group in the late '50s and through the '60s). He said that, in the '70s, he listened to Fleetwood Mac, and hearing Lindsay Buckingham’s playing inspired him to take up the electric guitar and try his hand at rock (Stewart had been purely acoustic/folk up to that point). He wrote some rock songs and put a band together, and showcased his new songs at a record company party. On stage, he explained how Buckingham had inspired him to pick up the electric guitar. He said this not realizing that Buckingham was in the audience. After he played his songs, Buckingham approached him, in awe, and explained that it was Stewart’s playing on Kingston Trio records that had inspired him to learn to play guitar in the first place!
I think it’s worth noting that “influenced by” does not mean “sounds just like”. Every musician has multiple influences, and any musician worth their salt will take all those influences and combine them into their own unique style. In my case, while Geddy was my original inspiration/influence on bass, I’m also influenced by Steve Harris of Iron Maiden & heavy metal in general, the disco that was popular before I ever picked up a guitar or bass, country music, the jazz I played (on alto sax) in junior high and high school, and even the orchestral music I played on bassoon in high school and college. All of that varied musical experience has had an influence on how I play the bass guitar. If somebody asks who my biggest influence is, I have to say Geddy Lee (and give a strong nod to Steve Harris), but when I actually play my original stuff I don’t sound anything like either of them. My own stuff is a conglomeration of all of my influences and my own personal take on them.
There’s no denying that Rush has kept their sound current by borrowing from new styles. But through it all, their songs are still instantly identifiable as “Rush” (even before Geddy’s vocals come in). This is quite different from other similarly-long-lived bands who are instantly identifiable because they keep doing the same thing they’ve always done (Rolling Stones, AC/DC, Aerosmith…)
Rush has also been a technological pioneer, being amongst the earliest adopters of digital recording technology and keyboard sequencing.