SharePoint Exception: The request uses too many resources can occur if too many commands are executed while calling ExecuteQueryAsync function. Resolution is to up default resource boundaries for SP WebApp.

Get-SPWebApplication | %{$_.ClientCallableSettings}

This script outputs informations about resource boundaries for your SP WebApps on local server.

$webApp = Get-SPWebApplication "<SITEURL>"
$webApp.ClientCallableSettings.MaxObjectPaths = 2000
$webApp.ClientCallableSettings.MaxResourcesPerRequest = 50
$webApp.Update()

(Note: These settings are unavailable on SharePoint Online, so you must execute multiple queries with JSOM)