$500 voucher to travel a few hours earlier seems quite a reasonable compensation
That it called you in advance and gave an option to reroute is better than just downgrading
You do not have to use the vouchers and can just cease flying AA , as you intended - or maybe you can use the voucher for someone else who wants to travel
Having to make a call to change a taxi booking to an earlier time and another to let someone know of earlier arrival time, does not seem to be a major issue - and hardly "scrambling"