You know this comment is not true. Margaret Court is a perfect example of this she won 24 slams YET people dismiss Court as GOAT because she won 11 grand slams at the Australian Open. The Australian Open was so unimportant that from the 1960s up to the late 1980s, players regularly SKIPPED the Australian Open they couldn't bother making the long trip to Australia.
It was only when the Australian Open got a roof did they elevate themselves upward. But still, the Australian Open is not as important as Wimbledon, French Open, or US OPEN. The other three slams count more they are TOUGHER to win and have a higher importance.
I cannot say whether you are being serious or just trolling, I hope the latter is the case (given the more or less exact same thread posted after the US Open as pointed out above)
But for the sake of the argument - what on earth makes this comment true?
"they (the others) are TOUGHER to win "
Why is that? The same players are playing and you need to win seven matches everywhere. If anything, AO is tougher to win as everybody (in theory) should be fresh and injury free after the offseason. And everyone can play relatively well on HC as opposed to both clay and grass.
And yes, the AO was less important 25 years ago. But now, it's more or less on pair with FO and US. The only one that sticks a bit out is Wimbledon as the grand price.
Finally, winning more AO's cannot hurt anyones legacy, only add to it. Diversifying your resume will add even more, but a slam is still a slam.