I don't think the Hernandez signing has had much influence over the ability to sign others. Especially when months prior to that McInnes had the chance to sign strikers but instead opted for Curtis Main.
Since finishing below Kilmarnock (a poor season where the decline was evident) he has had three transfer windows, and in Scottish terms has been handsomely backed.
Summer 2019: Ash Taylor, Curtis Main, Craig Bryson, Ryan Hedges, James Wilson, Funso Ojo. (Loans: Greg Leigh, Zac Vyner, Jon Gallagher).
January 2020: Dylan McGeouch, Matty Kennedy, Ronald Hernandez
Summer 2020: Jonny Hayes, Tommie Hoban, Greg Leigh (loans: Ryan Edmondson, Marley Watkins, Gary Woods, Ross McCrorie).
We were told this is the strongest squad since he took charge. Yet the team is the poorest in his time here.