We need to identify what physical quantity a light-year actually represents.
Time is a tempting choice because of the word "year", but the light-year is not measuring a duration, it uses one year only to fix how far light has travelled in that duration.
Light itself is not a quantity that can be measured in light-years, the term light-year is built from light's speed only as a tool.
Intensity of light is measured in completely different units, such as candela or watts per square metre, and has no link to the light-year.
Multiplying the constant speed of light by the fixed time of one year gives a fixed length, $d = c \times t$, and this length is what is called a light-year, used commonly to measure vast distances between stars and galaxies.