Trash Domain Or Redirect it (unmaintained)

[MyBambooSEO]

We have an old website with an old domain that has not been maintained for a few years; it now has a DA of 14 and a spam score of 24%.

Our current domain (same business) within a few years has a domain authority of 21  and page authority 29 spam score 1%. (Yes, this domain should have been redirected from the get-go)  The question is what do you do with it now? Toss it. Or redirect it. That domain has existed for years but still not sure what its value is from an SEO perspective. I would love to hear your feedback.

Is there any benefit to redirect the old domain to the current domain. Or is it a negative and what impact?