Retrieve all unique permissions of all folders in SharePoint libraries - powershell

Question

I am trying to generate a report with all unique permissions in all folders of a SharePoint Online library (and not user permissions, the goal is to retrieve group permissions). I wrote a Powershell script using SharePoint PnP. Please see below.
$permissionCSV = "path-to-csv.csv"
$CAMLQuery = "<View Scope='RecursiveAll'><RowLimit>5000</RowLimit></View>"
$items = Get-PnPListItem -List "My-List" -Query $CAMLQuery
$ctx = $Get-PnPContext
foreach($item in $items) {
if(item.FileSystemObjectType -eq 'folder') {
Get-PnPProperty -ClientObject $item -Property HasUniqueRoleAssignments
if ($item.HasUniqueRoleAssignments) {
$ctx.load($item.RoleAssignments)
$ctx.load($item.Folder)
$ctx.ExecuteQuery()
foreach($RoleAssignments in $item.RoleAssignments) {
$ctx.Load($RoleAssignments.Member)
$ctx.Load($RoleAssignments.RoleDefinitionBindings)
$ctx.ExecuteQuery()
foreach($RoleDefinition in $RoleAssignments.RoleDefinitionBindings) {
$RoleDefinition |
Select #{expression={$item.Folder.Name};Label="Name"},
#{expression={$item.Folder.ServerRelativeUrl};Label="Path"},
#{expression={$RoleAssignments.Member.Title};Label="Role"},
#{expression={$_.Name};Label="Permission"}|
Export-CSV $permissionCSV -Append -Force -Encoding UTF8 -NoTypeInformation
}
}
}
}
}
This code works. However, because our library is very large (more than 5000 folders), such a script would take days to be executed. So I am wondering if I am taking a wrong approach. All the posts I read only mention this method, which requires network communication for each single folder...
Does anyone knows the best way to generate such report without taking days? Any idea is welcome, including using other programming languages, but I would like to avoid paid third-party services if possible.
Thank you for your help.