Delete rows which do not meet specific criteria (text values)

You might find this faster than looping

Sub DeleteRows()
    Dim LastRow As Long
    
    LastRow = Range("D" & Rows.Count).End(xlUp).Row
    Range("K2").Resize(LastRow - 1, 1).Formula = "=IF(OR(ISNUMBER(SEARCH(" & Chr(34) & "ELF" & Chr(34) & ",D2)),ISNUMBER(SEARCH(" & Chr(34) & "OLEP" & Chr(34) & ",D2,1)))," & Chr(34) & "DELETE" & Chr(34) & ","""")"
    With Columns("K:K")
        .AutoFilter Field:=1, Criteria1:="<>"
        Rows("2:" & LastRow).EntireRow.Delete
        .AutoFilter
        .Clear
    End With
End Sub

Change Columns("K:K") & Range("K2") to suit a spare column in your sheet.