Understanding package management systems for Linux

I have a low-end laptop and am looking to install a lightweight linux distribution on it, but I have certain requirements regarding package management systems, since I will be contributing to a web development project.

I'm looking at Elementary OS which is a Debian distro (like ubuntu), and it seems I can use the apt-get package management system, which is really important for me.

That made me curious. I was looking at Solus OS (which I know isn't super lightweight), but it is also a Debian distribution.

However, the package management system on Solus is eopkg, and I'm wondering why I can't use apt-get.

Since the Debian package manager is dpkg and apt-get is derived from that, why can't we get apt-get on Solus OS? Or can we?

Thanks for any answers in advance!