If marketing campaign effect is low (blue) does it mean that product image is growing slower or that the customer is not interested in the product image?
Low refers the effect being small.
Be it marketing campaign effect, market growth rate, price elasticity, etc., low means the differential is small and high means the differential is big. So yes, “low” means the customer is not that much impacted by the product image to buy, therefore, don’t
expect the high rating of product image to bring you big change in sales. It follows therefore that a big investment to try improving product image may not reward you all that much.
Also, investment is relative. You may think you have invested a lot, but the competitor who invested even more get higher rating. It follows that you may get little effect even though you may have invested a lot because you competitor is investing against you.
It makes little sense to compete with the competitor for higher rating in a market that the effect of the rating is “low”.