Battles in the late 18th century were scarely more 'long ranged' then those in the early 18th or the 17th. Pikes had been largely abandoned by the 1700s, though the emphasis on big, tight formations stayed a lot longer. The thing with grenades was that they were dangerous as hell, and lighting and throwing one in the heat of battle wasn't really...effective. . I believe they were still used at sieges and naval warfare, though not much.
The status of grenadiers stayed a lot longer, of course. Even in the early Napoleonics, many grenadiers, especially from the HRE or Italian nations, still wore the lighter on their crossbelt.