Kern only came into power in May, the social-democrats (SPÖ) have been in a "great coalition" with christian-democrats (ÖVP) since 2007. This coalition has been on rickety legs for many years now and there's not much the two parties agree on. There have been no noteworthy reforms for a decade.

There's also the threat of the populist far-right FPÖ, which has been gaining power again after two failed coalitions with the ÖVP 15 years ago (The FPÖ have been polling at ~30% for several months now, which is the largest approval of all parties).

Several members of the ÖVP-government and regional bodies are actively working against the great coalition and undermining the head of the ÖVP, sympathising with going back in a coalition with the fascists.

For all these reasons, Bundeskanzler Kern is not as powerful in legislature as would be desireable. Also I understand his remark as suggestion for a discussion and possibly a proposal for an EU-wide discussion on unifying tax laws. And he's probably fishing for votes with public statements on popular topics.

Personally I think he's the most promising Bundeskanzler we had in a long time, as he's an intellectual and is charismatic enough to potentially neutralize the threat of a far-right government.