It is possible that your loved one is not interested in going on outings with you because they are too overwhelming. If you can plan activities that are not over stimulating or that create anxiety that would be helpful.
Think about the things your loved one has enjoyed doing throughout their life. Some of these may need to be modified because they will no longer be appropriate. For example, they may find large numbers of people too much to mange now. Think about how you can do a simplified version of what they have always loved.
It is very important for people with dementia to be socially and mentally stimulated.