Is it important that singular subjects be matched with singular verbs

Yes, it is very important. In grammar, there is something called subject verb agreement. It means that the subject must be in harmony with the verb. For example, if one writes, SHE LIKE TO EAT PIZZA. The personal pronoun SHE does not match with the verb Like which must be with the letter S (LIKES). So, it should go like this: SHE LIKES TO EAT PIZZA. For instance, it is very important that we pay a lot of attention when writing, if not, our writing could be poor and grammatically incorrect.