The way my pediatrician explained this to me, and she is a former LLL Leader and supports extended breastfeeding and self weaning, is that in the second year, kids tend to eat less because they are too "busy" to settle down for meals. Offering healthy snacks frequently makes a huge difference.
She also said that they do eat more than you think, and as long as baby's weight is ok, he/she is getting enough food.
Her suggestion for trying to increase solids intake, if you want to, is to not offer the breast before mealtime unless LO wants to nurse. If it's lunchtime, go ahead and offer finger foods, and after LO has eaten and played and lost interest, then you can offer the breast.
Breast milk is still an excellent source of nutrition for a toddler and can be their sole source if necessary, but it is even healthier, since we have such great access to healthy foods, for baby to have exposure and daily servings of a wide variety of foods.