The argument against a new campaign is, roughly, this. The dissident republicans have no hope of achieving what the Provisional IRA failed to achieve in thirty years. We will understand what viable objectives the dissidents might have if we understand what is wrong with that argument. The Provisional IRA failed to achieve a united Ireland but succeeded greatly in the secondary objective of stalling all political compromise in Northern Ireland until it was ready to participate itself. No attempt at a settlement could work until they permitted it to work. Their campaign presented a veto rather than a demand.
And what about those republicans who are now sceptical of power sharing but do not support the dissidents; those who have been with the peace process so far? Is there a danger that they will be disillusioned and will defect to support a growing dissident campaign? Well, they are miffed that Sinn Fein has been humiliated in its power sharing relationship with the DUP. And they surely can not be much impressed with the Sinn Fein claim to be providing a route to a united Ireland. This is the weakness in the Sinn Fein position; it actually has virtually no chance of uniting Ireland. Then again, neither have the dissidents, though they might aspire to scuppering the Sinn Fein project and see that, at least, as progress in the right direction.
As I said, there are legacy issues for Sinn Féin..