“This was version 2.something when I started, I’ve been working on this for n years and it’s still version 2.something” sure sounds like a demotivating feeling to me, too.
If I worked on a product that was version 2.1 when I started, and 5 years later was on version 6.5 without any actual rewrites or improvements in it, I would find that just as demotivating.
Such a stable environment would leave a lot of room for side projects on a stable paycheck, or getting some extracurricular qualifications.