This is not my field, though it interests me greatly...
The standard model includes Electromagnetism, the Weak and the Strong forces but does not include gravity.

A 5th 'force' could be the missing puzzle piece that lets us fit it all together.

Right now we have the Standard model, and we have general relativity - The standard model does an incredible job, not just explaining what we see in particle physics, but making predictions of new particles that are subsequently verified. In its domain of the Electromagnetic, strong and weak forces it seems flawless.

Same for general relativity- it unquestionably describes the cosmos extremely well.

But unifying all the forces has resisted countless geniuses... it is hoped that something can be seen that is outside the standard model that will point us to the path to unification.

That is why this discovery- if true- would be so important.

We know there are large gaps in our understanding- what is dark matter? This might shine a light and help us figure out the path to explore.