The question is based on the incorrect assumption that beneficiary applies only to people or to legal inheritance as a result of death.
The following is one of the senses used by Merriam-Webster to define beneficiary:
1 : a person or thing that receives help or an advantage from something : one that benefits from something
// The college was a beneficiary of the private grant.
Synonyms for this particular sense, as well as words with related grammatical functions, include the following words: recipient, receiver, advantaged, advantage, benefit, benefited, profited, bettered, aided.
As such, the example sentence (which I will paraphrase slightly) can still make use of beneficiary—as well as the related benefit, depending on the specific nuance being conveyed:
The beneficiary of resolving software bugs is reliability.
The benefit of resolving software bugs is reliability.
Other example sentences where beneficiary is used in the sense of a thing gaining an advantage follow (the emphasis is my own).
From Department of Energy: Implementation and Use of Other Transactions Authority Provided in the Energy Policy Act Of 2005 by Gene Aloise:
The beneficiary of contracts is the federal government.
From Licensing Royalty Rates by Gregory J. Battersby and Charles W. Grimes:
Active Video argues that Verizon is not an intended beneficiary of the TV Guide agreement, which was a joint development agreement between Active Videos predecessor and TV Guide to produce a specific product.
From Nanotechnology: Social Implications II edited by Mihail C. Roco and William Sims Bainbridge:
In any case, virtually all models of technological change predict that the main
beneficiary of technological improvements is the most inelastic factor of
production. In the modern world. where the supply of labor is inelastic relative to
the supply of capital and where the supply of economically useful natural
resources has increased as a result of the discovery of new sources of natural
resources and/or development of substitute resources, this makes labor the main
beneficiary of technological advance.
From A History of Cornwall by Morris Bishop:
In other states their university is the beneficiary of the state; here the state is the beneficiary of the university!
From In Praise of the Beloved Language by Joshua A. Fishman:
As the symbol of the conjoint attainment of literacy (cultural refinement and autonomy (cultural independence), the written language is commonly the ultimate intended goal and beneficiary of all modernity-oriented corpus planning initiatives. This is not to say that only the written language is the object or beneficiary of such planning, but were such a view to be advanced—and it has been—it would be an exaggeration whose point had much to be said for it.