Bootstrap has been around for a while. It has a vast community and much probably will not be gone in a while. Integrating Bootstrap into a new or existing project is super easy. we can get started by including the CDN or downloading the source file(s) and linking them in your markup page.
But nowadays there are a lot of libraries available that make the work more easier.
1) Tailwind CSS
 Tailwind CSS id a trendy framework when it comes to developing Frontend websites. Tailwind is a good solution if we need a sleek design, a user interface where building with components will be important (because tailwind strongly favors component-based UI), and we know we will need to extend the built-in classes with our own (because tailwind is very easy to extend)
Put simply, we should use Tailwind regardless. It is a great addition to whatever we use because it removes the hassle of writing CSS.
2) Material UI
It is used by Nasa, Amazon, Unity, Google and all its products. As it uses 12-column grid system, provides a fully responsive design. Mobile-first and very user-friendly, but UI can be overwhelming with animated interactions for desktop. The development speed is less than bootstrap offers, but can be increased by using templates. Provides unique easy customizable design.
3) Skeleton
Skeleton is a simple, responsive, lightweight boilerplate and a CSS framework. It consists of a 12-column fluid grid, consisting of rows and columns. It is built keeping in mind the mobile framework. It is easy to start and needs the least compilation. It is best for a small project since it styles only major standard HTML elements and considers a grid.
4) Bulma
Bulma is a modernized CSS framework that is free, open-source, and offers competitive frontend components. It needs no prior knowledge of CSS framework and developers can easily create responsive web interfaces. It has a comprehensive flexbox grid, a wide range of colors and helps in building good-looking websites with ease. It is rich in components, modular, easy to learn, compatible, well documented, and constantly enhancing. Hence, it is sought after by developers.
5) Pure.css
Pure.css is apt for small projects since it has a bunch of CSS frameworks clustered together. Since it is designed especially for mobile devices, it helps developers build responsive layouts with the use of grids, menus, forms, buttons, etc. Despite being tiny in size, it offers great performance and output. It keeps file sizes small, and each line of CSS code is done with care. It has minimum styles and makes developers write the application styles on top of it. Elements created by Pure look good on all screen sizes. Pure has a flat design and hence it is simpler to append newer CSS rules. With just a few lines of CSS code, the entire appearance can be customized.
In this era, we can identify that there are bunch libraries that can be used in terms of frontend development that are much more efficient, flexible and rich in components than Bootstrap. Therefore by concerning the requirement, we can choose an option without just being limited to bootstrap.
