I’ve been keeping an eye on the people in my life who are really effective decision makers. Two of the underrated capacities that underpin their successful processes are quite simple: 1) they carefully keep track of decisions that need to be made, and 2) they actually make the decisions on their decision list, even if they have incomplete information. The first capacity is organizational; the second is behavioral.
So, if you think of yourself as a bad decision maker, try keeping a decision list each week and picking a weekly, recurring time (preferably early in the day) when you make as many of those decisions as you reasonably and responsibly can. See if that changes anything for you.