Simon Brooks seems to have answered his own question.

The LibDems over at Subordinate Central shared the  The Western Mule  delight in reportimg that a former activist, asked  whether Plaid Cymru have given up Welsh nationalism to become just ‘a generic British anti-austerity party’?

In an article for the current affairs magazine Planet, Simon Brooks – who founded the Welsh language communities movement Cymuned and is the author of several books on Welsh cultural issues – suggests that the cause of Welsh nationalism has become subsumed within what he calls “a pan-British anti-austerity radicalism”.

He writes: 

“Opposing fracking, standing up to the cuts, support for the latest public sector strike: these are worthy causes, but British in character and the word is not meant in any pejorative sense.
“There is a failure here to develop a national narrative.
“The image of political hugging on the stage during the leaders’ debates [when Plaid leader Leanne Wood, SNP leader Nicola Sturgeon and Green Party leader Natalie Bennett had group hugs], the ‘anti-austerity alliance’, is the image of a nationalism which is a point on the political compass of a wider British radicalism rather than the compass itself.
“Nationalism has become party to a pan-British radicalism, and generous towards those who reject the national cause.
“This was an election in which Plaid Cymru embraced a party, the England and Wales Green Party, which was standing against its own candidates, including in Ceredigion, its main target seat.”
According to Brooks, there is nothing new in what he calls Plaid Cymru’s new-found interest in the British Left: “Making common cause with English radicals has been the bulwark of every Welsh general election campaign since 1968.
“This alliance delivered to the Liberal Party its hegemony between 1862 and 1922 … and to Labour its hold over anglophone Wales up to the current day.
“By becoming Old Labour Lite – that is, by portraying Welsh Labour as Red Tories, and Welsh nationalists as inheritors of Lloyd George and Nye Bevan, the Party of Wales hopes to inherit the radical crown.”
But, Brooks argues, the strategy contains within itself the seeds of its own destruction.
“Civic nationalism” of the kind being pursued by Plaid does not differ from similar approaches in England and the wider UK, and therefore there can be no logical reason to press for the break-up of the UK.

He writes 

“In its argument for progressive British politics, Plaid Cymru may well be undermining ‘Red Tories’, but it is making the intellectual case for the continued dominance of an improved Labour Party in Wales.”

 I was going to write a response to Simon Brooks article but it appears he has somewhat answered his own question. because today's Wasting Mule online reports that Simon has rejoined the Party and his reason for doing so is interesting

.
He said:

 “I’ve rejoined Plaid Cymru and feel a lot better for it. I think it makes total sense for Plaid to be anti-austerity. My concern was that the party needed to focus on why cuts were bad for Wales specifically.

“In Gwynedd, where I live, we are of course very dependent on the public sector for employment, and cuts are damaging our communities.“I have known Leanne for 20 years and in this part of Wales she is regarded as something of a rock star.”

It just goes to show that a critical analysis of a approach does not necessary mean that it is the wrong one only that it may lead you away from your ultimate goal.