Self improvement is a marathon. You have to put in work every day to get results in the long term. It's like putting one foot in front of the other if you want to run a marathon.
Learning something or getting better at a skill at the pace of just 1 thing a day is immensely powerful. You could read a bit, meditate, learn something new or workout.
Some people just think it's too much work or decide it's not for them, but the wonders of personal development are easily accessible if you just start.