Why the sheet looks plain
Most printable habit trackers are designed to be pinned, not used. Mandalas, watercolour borders, a quote across the top. They look good on day one. By day nine the boxes are too small to tick with a biro, and there are only 28 of them because the layout ran out of room.
This one has a column for every day of the month you pick, a weekday letter under each date, and a heavier line where each week starts. Weekends are lightly shaded. That is the whole design. Everything else on the page is room for your pen.