Is there an intermediary between developing a custom UI-library and committing to someone else’s library?

At my company we are a small team (not startup), our flagship product is desktop and hardware-based but we also have our own online platforms (store, user portal, and other new things to come) plus a marketing website. In terms of website our design tends to be similar to apple, when it comes to web apps we are using lots of ideas from material design but not completely following them.

We need to develop a design system / UI library with reusable components because inconsistency is getting out of control. Initially, we thought about using bootstrap and develop a custom theme on top of it. However, after talking with some front-end dev friends they recommended developing a design system / UI library from scratch.

Is there a middle ground between bootstrap and a design system from scratch?

We are also concerned about consistency between a website and these other systems. I know that websites (information software) are different than the application (information software), but we will try to make at least typography, forms and icons consistent. But since our design team has only 2 people we can't "scale" design and because engineers have no UI kit, unified design system or guidelines to work with things get out of control.

It looks like the downside of bootstrap is that it's too opinionated, heavy and customization might cause problems with overrides and updating to new versions of the framework might also cause it to break.

On the other side, developing from scratch is an ideal situation if we had lots of time and resources, which we don't have. As I said most programmers here are back-end C++ and we only have 2 web devs to develop lots of systems. Some of them like the store we will be using some open source shopping carts for example.