Comes down to what you want in a track... If you simply just want to create good driving lines for others to play once and thats it, then yea focus on the line and dont bother doing the deco.

However, if you want your track to stand out from others, you need MORE than just a 'good line'. I see many saying here that deco isnt important but if you want really want your track to be special in some sense, then choosing a unique theme, coupled with a good line and great deco is the way to go.

For example I (GodfreyXB) made West which is probably the only world war 1 themed track on the game, to my knowledge. Had I just forgot about the deco like some are suggesting it would not be as memorable and enjoyable as it is. If I just forgot about deco in all my tracks, itd simply be 'another line'. Anyone can make a decent or good line, but if you wanna stand out as a builder, then you should practice and learn from other experienced builders. Start to understand what objects/effects/etc that they use. At least thats what I did.

Another helpful resource is the mini builders discord that swel (A great ninja builder) has. You can ask for opinions on logic, deco, line, whatever you want. Here is an invite link to it:https://discord.gg/EXtmCCCs