What were the reasons why the period really may not have been the "Era of Good Feelings?"
The name “Era of Good Feelings” is often given to the time that began with the first election of James Monroe in 1816 and ended with the creation of the Whig Party. At times, the term is used only to refer to Monroe’s time in office.
Either way, there are two main reasons why this time period should not really be called the Era of Good Feelings.
First, there is the fact that slavery and sectionalism were alive and well as issues that were dividing the country. The name for this era implies that everyone was on the same page politically and there were no really important disputes. This is belied by the fact that slavery really was a big issue. This was, after all, the time when the Missouri Compromise became necessary. Thus, the slavery issue was lurking.
Second, even if there were no formal political parties to oppose one another, there was a growing divide between informal political factions. The 1824 election was to end up being very rancorous. It ended with the “corrupt bargain” controversy that led to hatred between the supporters of Adams and those of Jackson. Even with only one party, there was still political discord.