Plural search term leads to a single product instead of category

I have noticed this many times on my site for year randomly but noticed it with a one of my competitor's too. Lets say a customer searches for "wood widgets" (just a made up example), the results will show for a single page of a wood widget product I offer on my site instead of my category page where I may have tens if not hundreds of wood widgets. I have noticed one of my competitors is killing me in my rankings but their site has the same issue. Many of our competitors have results for their category pages instead of a single product. It seems odd that Google just hopes this one product is what customers want to see. Or maybe this is their plan? Anyone else seeing this or know how to fix? I should note that my site still shows up with a lot of top results in shopping and images on the front page with some of my category pages towards the top of page 1. My site is almost 25 years old, with almost 20K products and several are added per week if not daily. But the last few months ranking have started to fall off.