There is very little truth to them. Soldiers may put up with one or two mid-ranking officers who are incompetent or cowardly, but wouldn't if such attitudes were rampant amongst the officer class. That's true of soldiers from any era, including the "age of gunpowder."

It's certainly true that society during the Early Modern period was very different from today's, and that led to behaviour which we might view as pompous or ridiculous in a modern light. At the battle of Fontenoy in 1745, for example, British and French regiments refused to fire at one another until the other had fired first. The account of that incident is by Voltaire, and may not be true, but at the very least it's indicative of the mannerisms of the times.

It should be stressed though that such "foppish" behaviour was an exception to the norm. The officers of standing European armies from the 17th century onwards were professionals, trained to lead their men in complex battlefield situations and schooled in how to maintain both discipline and morale. The swelling size and effectiveness of Early Modern armies meant that leaders as brave and bold as any throughout history were needed if they were to be effective.

Nor were all officers wealthy or aristocratic. Whilst the equipment and training all came at a high price, and thus ensured most officers were from the landed classes, there were plenty who also rose through the ranks from humble origins. In both the Dutch and French armies there are stories of pikemen rising to become Field Marshals.

In short, armies could not possibly have functioned as effectively against one another as they did if the cliched modern view of 17th - 19th century gentry was accurate.

Sources: Thomas M. Barker: Army, Aristocracy, Monarchy.

J. R. Hale: The Military Education of the officer class in Early Modern Europe.

J. Chagniot: The ethics and practice of war amongst French officers during the seventeenth century.