How can you assert that the end quality is stuck at the same level when we literally had a massive leap in quality within 4 months? chatGPT with 3.5 was releas

How can you assert that the end quality is stuck at the same level when we literally had a massive leap in quality within 4 months? chatGPT with 3.5 was released in November 2022. 4 in March 2023. Massive leap in quality between the two relases.