You need a paid membership to Nintendo Switch Online to play course world in Super Mario Maker 2. Pretty sure you could access course world at no extra cost in the original
Nintendo Switch Online and microSD on Amazon for 50% off | CNN Underscored
Nintendo 64™ - Nintendo Switch Online - Nintendo Official Site
Nintendo Switch™ Mario Kart™ 8 Deluxe Bundle (Full Game Download + 3 Mo. Nintendo Switch Online Membership Included) - Nintendo Official Site
A new Nintendo Switch Online membership plan with expanded benefits is coming - News - Nintendo Official Site
Buy Nintendo Switch Online 12-Month Individual Membership from the Humble Store
Nintendo Switch™ Online App for iOS/Android - Nintendo Official Site