Aussie Rules is a direct descendant of Gailec Football for mine.
I mean the general rules are exactly the same with the only change being a rugby football and tackling.
There's even less evidence for that than Marn Grook having an influence.
Modern Gaelic football first started appearing in the 1870s, 11 years after Aussie Rules was codified, and wasn't codified until 1884, 25 years after Aussie Rules and 4 years after Wills died.
Caid (the Irish equivalent of Shrovetide games that predated Gaelic Football) weren't particularly similar to what became Gaelic football either. There's also less reason to believe that Wills encountered any of the Caid games than Marn Grook, with only a handful of accounts of any of them being played in Australia on gold fields in SA and Vic that we know for a fact that Wills wasn't present to witness, and they certainly weren't ever played regularly in England, let alone when he was there.
The original rules of Gaelic football being almost identical to the Melbourne rules (i.e. Aussie Rules) of the time has actually lead some to suggest that Irish immigrants that had returned from Australia influenced Gealic football's rules, not the other way around, but again the evidence is circumstantial at best. In other words there's about as much evidence for that hypothesis as there is that Marn Grook inspired Aussie Rules.
Edit:
Turns out that I should have updated my knowledge before talking about this subject.
Direct evidence has been found in the last 10 years that the GAA copied rules from Victorian Rules rulebooks of 1860-70s verbatim, and there's even paperwork from Limerick that states that they adopted some of the Victorian Rules.
Many of those rules have been removed from the rule book over time, and pretty much all of those that were left have evolved in completely different ways in Ireland than they did down here, but Aussie Rules did directly influence Gaelic Football and not the other way around.