The proposed cross-hemisphere competition bit the dust when the Sharks, Stormers, Lions and Bulls were not granted permission to travel to Europe.
Warburton, the former Cardiff Blues and Wales flanker, said the Pro14 had turned into a “mish-mash” and called for a return of the Celtic League.
Italian and South African teams have been added to the competition in recent years but the two-time Lions captain would prefer it to revert to the core clubs from Scotland, Wales and Ireland.
“I’m not going to lie, I think the whole Pro14/Rainbow Cup has turned into a mish-mash competition,” he said at Canterbury’s launch of the new British & Irish Lions Test jersey.
“I think you need to keep your domestic league. Ideally I’d have it as a Celtic league. I think the Italian teams should go into the French league, it would be much better for them logistically and I’d think they’d agree with that.
“Obviously the ideal situation would be a British and Irish league but I think the brutal fact is that England don’t need the Celtic teams.
“But I think the Pro14 is changing every year and it’s almost just like shamelessly going wherever the money’s at and not where the best quality product is going to be.
“For me personally, I’d much rather watch Welsh teams play each other and Irish teams play each other. I think they’d be better games to be honest.”