Query to get years as list of values

WITH years
     AS (    SELECT ADD_MONTHS (TO_DATE ('01-01-2020', 'DD-MM-YYYY'), LEVEL * 12) year
               FROM DUAL
         CONNECT BY LEVEL <= 30)
  SELECT TO_CHAR (year, 'YYYY') year
    FROM years
   WHERE year < TO_DATE ('01-01-' || TO_CHAR (SYSDATE, 'YYYY'), 'DD-MM-YYYY')
ORDER BY 1 DESC;

Script Output

Year

2023

2022

2021