"...decisions made by the council prior to your appointment are still valid decisions..."
Unless or until they are reversed by the incumbent council - historic decisions / policies / procedures are not set in stone, they are determined by the incumbent council.
Cllrs need to have the strength of conviction to change that which may be considered to have been historically inadequate rather than simply roll it forward as established precedent.
An early agenda item to review / amend / renew / retain existing policies and delegations is a pretty good idea after a significant change in personnel.
This may be especially true if we draw the assumption from the OP that there has been a significant change in Cllrs including co-options - which in and of itself is often an indicator of a poorly performing council.
Ring the changes!