Help with a formula to count specific cells, while excluding certain text - Google Sheets

Hey Excel Forum, hope you can assist with this issue.

Im pretty OK with excel, but for some reason I cant figure out this formula.

Im trying to make sense of counting specific cells, with excluding certain text.

Ive been using

=SUMPRODUCT(--(D18:D54<>""),--(D18:D54<>"OFF")) - but the SUMPRODUCT doesn't allow me to skip rows, and I have data in between each row which I dont want included. Ive tried the COUNTIF formula as well, but no luck, as it throws errors.

I know I can make additional rules for the SUMPRODUCT by continuing the formula and changing the criteria I need excluded, but the criteria changes a lot per column, and changes frequently, and it'll be a lot to continue to update.

Im using Google Sheets.

Added to the sheet you linked above.

Essentially I'd like it to count the cells in each column, while skipping the row of availability. I eventually got it to work by just adding more criterion to the SUMPRODUCT function, but due to the large amount of variances I have to exclude for availabilities it makes it pretty tedious.