Retinol for my mom

Hii

My mom is 67 years old. She has been suffering from a lot of sun damage/hyperpigmentation/ uneven skin tone since 35 years. She doesn't want to see a dermatologist so she started using encapsulated retinol 1% since 1 month (from advanced clinicals brand) with absolutely no irritation. She started gradually and then daily. She hasn't seen any improvement yet even though the percentage of retinol is high. Any thoughts why could that be ?

Thanx 💗