General Sun Yi was a founding lieutenant general with the seniority of a general, why did he say this?

To briefly introduce his resume, he served as chief of staff of the Red Army Division in 1931; in 1936 he was promoted to chief of staff of the Red 1St Corps; during the War of Resistance Against Japanese Aggression, he served as chief of staff of the 115th Division Brigade, chief of staff of the Jin-Cha-Ji, and principal of the Kang Da Branch School; during the Liberation War, he served as commander of the Jizhong Military Region, commander of the Seventh Column of the North China Military Region, and commander of the Supplementary Training Corps of the North China Military Region.
Sun Yi once held a position in the Northwest Army, higher than Li Da, who was later awarded the title of general, and served as a lieutenant colonel's staff officer. Don't look at Sun Yi as a staff officer, before joining the Red Army, he did not participate in many battles in the Kuomintang troops.
After the Ningdu Uprising, he followed Zhao Bosheng to the Red Army and was given a better position, chief of staff of the division. Perhaps when I first arrived at the revolutionary contingent, I was fundamentally different from the old troops, and I was always very confused in my thinking, and I wanted to go to the Red Army school to improve, but after many applications, I was agreed.
When he went to the Red Army School, he became a teacher and found direction and fun. After working for more than two years, he was transferred to the front line and then served as the chief of staff of the division for half a year, and then he had to apply to return to the school as a teacher.
The second time as a teacher was not long, and soon began the Long March.
On the Long March, he served as the chief of staff of the instructor, the chief of staff of the defense regiment, the chief of the regimental education section, and the chief of the operations section. After arriving in northern Shaanxi, he served as deputy chief of staff and chief of staff of the Red 1st Army.
Of these positions, he worked in the education section for the longest time, while the rest of the posts were held for only a few months. Don't look at him as the chief of staff of the Red 1Stour Army, when the troops had already arrived in northern Shaanxi and experienced the most tragic stage. In staff positions, he participated in many battles under command.
During the War of Resistance Against Japanese Aggression, he served as Chief of Staff to Nie Rongzhen, which was very difficult. Especially after the Jin-Cha-Ji anti-Japanese resistance behind enemy lines, the situation was very grim, and it was necessary to think that the military-style and tough chief of staff assisted him, he was somewhat incompetent, and Nie Heting took over his post.
Later, during the War of Resistance Against Japanese Aggression, he served as the principal of the Kang University branch and began to do education. At the end of the War of Resistance Against Japanese Aggression, he went to the Jizhong Military Region as chief of staff, and the plate was smaller, and the ability was naturally matched.
During the Liberation War, he served as the commander of the Jizhong Military Region and later as the commander of the column of the North China Military Region. Although he became the chief officer of the combat unit, there were not many wars. In 1949, he was transferred to the commander of the Supplementary Training Corps of the North China Military Region, and the original battlefield sent soldiers to the main force.
A highly qualified general like Sun Yi could have made great achievements in the course of decades of revolution, perhaps because of the ability problem, he has been standing still, or even going downhill.