Excluding Folders with Get-ChildItem - Need Help Debugging a Script

I've searched through both StackOverflow and SuperUser to try to figure this out, and I'm still getting plagued by a problem I can't figure out how to fix. I know it's something simple, but after playing with it for an hour I'm still stumped. Simple question: how the heck do I tell Get-Childitem to exclude folders?

Right up front here's the code that doesn't work:

$sourceDir="E:\Deep Storage"
$targetDir="W:\Deep Storage"
$excludeThese = 'Projects2','Projects3','Projects4';

Get-ChildItem -Path $sourceDir -Directory -Recurse | 
  where {$_.fullname -notin $excludeThese} |
    Get-ChildItem -Path $sourceDir | ForEach-Object {
        $num=1
        $nextName = Join-Path -Path $targetDir -ChildPath $_.name
    
        while(Test-Path -Path $nextName)
        {
           $nextName = Join-Path $targetDir ($_.BaseName + "_$num" + $_.Extension)    
           $num+=1   
        }

        $_ | Move-Item -Destination $nextName -Force -Verbose -WhatIf
    }
}

The underlying concept here already works:

$sourceDir="E:\Deep Storage"
$targetDir="W:\Deep Storage"

Get-ChildItem -Path $sourceDir -File -Recurse | ForEach-Object {
    $num=1
    $nextName = Join-Path -Path $targetDir -ChildPath $_.name

    while(Test-Path -Path $nextName)
    {
       $nextName = Join-Path $targetDir ($_.BaseName + "_$num" + $_.Extension)    
       $num+=1   
    }

    $_ | Copy-Item -Destination $nextName -Verbose
}

Basically what this does is it moves folders from one place to another, and if files exist in both places, it renames files coming in. It helps keep my archive drive clear. But there are three folders there that I want to exclude because I still pull assets from them regularly, so I don't need those files moved.

Hence the difference between the two code samples: in the first one, I'm trying to get Get-Childitem to exclude a specific trio of folders, while this second one just grabs everything all at once.

I tried just doing a straight -Exclude with $excludeThese as the variable, without success; I tried skipping the variable approach altogether and just putting the folder names in after -Exclude. Still didn't work. I also tried putting in the entire path to the folders I wanted to exclude. No good--no matter what I did, the -WhatIf showed that the script was trying to move everything, including the folders I was theoretically excluding.

The last trick I tried was one I came across here on SO, and that was to go a gci with the exclude argument first, then do another gci after it. That still failed, so now I have to turn to the experts for help.

I would use a regex string created from the (escaped) directory names to exclude to make sure files withing these folders are ignored.
Also, by using a lookup Hashtable of all file names already present in the target folder, figuring out if a file with a certain name already exists is extremely fast.

$sourceDir    = 'E:\Deep Storage'
$targetDir    = 'W:\Deep Storage'
$excludeThese = 'Projects2','Projects3','Projects4';

# create a regex string with all folder names to exclude combined with regex OR (|)
$excludeDirs = ($excludeThese | ForEach-Object { [Regex]::Escape($_) }) -join '|'
# create a lookup Hashtable and store the filenames already present in the destination folder
$existingFiles = @{}
Get-ChildItem -Path $targetDir -File | ForEach-Object { $existingFiles[$_.Name] = $true }

Get-ChildItem -Path $sourceDir -File -Recurse | 
Where-Object {$_.DirectoryName -notmatch $excludeDirs} |
ForEach-Object {
    # construct the new filename by appending an index number if need be
    $newName = $_.Name
    $count   = 1
    while ($existingFiles.ContainsKey($newName)) {
        $newName = "{0}_{1}{2}" -f $_.BaseName, $count++, $_.Extension
    }
    # add this new name to the Hashtable so it exists in the next run
    $existingFiles[$newName] = $true
    # use Join-Path to create a FullName for the file
    $newFile = Join-Path -Path $targetDir -ChildPath $newName
    $_ | Move-Item -Destination $newFile -Force -Verbose -WhatIf
}