The Septuagint, a Greek translation of the most significant Hebrew scriptures, completed by 100 BC at the latest, chose to translate 'elohim as αγγελους (that is, 'angels') in Psalm 8.5 (actually verse number 8.6 in the LXX). In the second half of the first century, the author of Hebrews cites the Septuagint translation exactly, reiterating the opinion that the 'elohim were understood as angels by at least some Jews over the course of at least two centuries.
So, at the very least, the more recent translations of Psalm 8.5 are not introducing an unsubstantiated take on the word 'elohim. Interpreting 'elohim in Psalm 8.5 as referring to angels has been done for more than two-thousand years.
In a similar issue of translation, Psalm 82.5 says:
'elohim stands in the assembly of 'el; he judges among 'elohim.
Even though the word 'elohim is used twice, the two instances are unanimously translated as referring to two different classes of entities, the former superior to the latter:
God stands in the divine assembly; he judges among the [gods / angels / divine beings].
This again displays an identification of 'elohim with 'angels'. But in at least one of the Dead Sea Scrolls, 11Q13, the human Melchizedek is also identified as the first of the two uses of 'elohim in Psalm 82.5, the one usually identified as capital-g 'God'.
But the key part of your question is:
Is this justified?
That depends on the semantic range of the word 'elohim.
In English, the word 'god' tends to be used in a very narrow manner. It is most often used in specific reference to the god of the bible, often called simply 'God' (i.e. YHWH, the God of Israel). The word is also often used to refer to a singular, all-knowing benevolent entity in a more general sense, with the god of the bible being implied at best. Either way, for most English-speakers, the word 'god' carries the inherent meaning that there is only one such being.
In Hebrew, the 'elohim word-family (e.g. 'elohim, 'eloah, 'el, 'elah) has a much wider semantic range. Beyond the obvious use of these words for YHWH, these words can be used for pagan gods, for angels, and even human rulers or leaders (e.g. Psalm 82.6, at least as understood by the author of John 10.34-35).
And the existence of texts like LXX Psalm 8.6 or 11Q13, cited above, are ample demonstration that 'elohim was sometimes understood by ancient Jews and Christians to refer to angels or humans, depending on the context.
So yes, the choice of translating 'elohim as 'angels' in Psalm 8.5 is justified. 'Angels' was included in the semantic range of meaning for 'elohim.