It is not so simple. If there is no change in Olympic dates, IOC/IFs need to check if there is enough time to hold all the qualification tournaments. For example in Boxing, they need to host continental qualifiers first and then the World qualifiers. Also, need to have sufficient gaps between those tournaments as well (specially considering that Asia/Africa already have had their qualifiers, so small gap will be beneficial to boxers from these confederations).
In case of rankings based qualification, they need to make a decision if there is need to postpone the deadline or not. For example, Tennis will be using rankings published on 8 June 2020. We have lost atleast 2-3 months of the tour. 3 months is 25% of the season. So, should ranking date be extended by say a month (unfair to those who got points in the corresponding period last year) or should they stay with the same ranking date (unfair to those who were chasing the qualification and were banking to get points in the last couple of months).
And in case of postponement to say 2022, obviously ranking issues remain. Also, how bad would it look on part of IOC and organising committee if 2021 World Champion in a sport can't take part but 2019 World Champion has qualified.
All in all, not easy decisions. Honestly, I don't think there is any decision which can be remotely acceptable/fair to all.