Knowing nothing of the circumstances in the video I wouldn't criticise the accordion player - perhaps they were making the best of what was available.
If a player of Irish Traditional Music on accordion doesn't use the basses, or hardly uses them, it's not a weakness in their playing, it's part of the musical genre which is primarily melodic. The tune should always be able to stand on its own.
Hi TomBR, I have often thought about what Irish music on the accordion actually is... I sometmes struggle for an answer beyond the obvious.
@Pipemajor made a solid point about Irish accordion players often not using the bass and following in the tradition of the melodeon etc. That seems to be quite common, especially with the small wooden instruments, like Saltarelle etc.
You also made the great point about the bass being used lightly to follow the Uilleann pipes.
My thoughts on Irish music, are perhaps outdated and follow from a Scottish dance music flavour - that of Irish Jigs, Reels and Waltzes being strict tempo for ceili dancing (like The Gallowglass Ceili Band) or more the accordion entertainer style music, Paddy Neary etc.
However, I recently heard this piece for the first time. A tune written for the accordion, called My Isle of Emerald Green:
I think it's lovely and has sophisticated (almost orchestral) interaction between the bass and treble. At what point does a tune become Irish or cease to be accepted as Irish? Is this Irish classical? Maybe it's a coincidence that the piece is played on an accordion and is about Ireland. Where is the idiomatic balance to be struck?
I don't know, just a thought...