With icon fonts such as Font Awesome, Material Design Icons and Glyphicons there’s certainly no shortage of icons for use in web applications.
Iconic and Feather are 2 alternatives to these widely-used icon collections. The latter is available for free under the MIT licence (a donation will be very much appreciated, though) while the former can be purchased for $129 ($39 for just the Webfont without SVGs) for a single app licence.
Both are framework-agnostic and Iconic in particular has been designed from scratch with the requirements of modern web apps in mind.