Absolutely NOT. You have many muscles in your body. Your heart is a muscle as well. Without exercise your muscles will atrophy. All sorts of health problems will follow and you will gain more fat more quickly than you did in the past. This is what many adults allow to happen and then excuse it by saying they're getting old. Certainly you don't want to weaken your heart and other muscles (and in turn weaken your health) by being lazy, right?
Further, when it comes to health you cannot judge a book by it's cover. There are thin and skinny people who have very serious health issues because they never work out. This is in addition to those who are obviously unhealthy and those who appear to be average.
Lastly, while light to moderate exercise is better than nothing you will not be improving your health unless you challenge your heart and other muscles regularly via strength training and cardio. It's fine to alternate between these on different days and these workouts can be done at home if needed. Also, you can break up workouts throughout the day to fit your schedule. NO EXCUSES! Your health is too important to be lazy about.