Not to nitpick, but P239s and, in fact, most Sigs made in the U.S. have alloy frames.
The all German older models were the all steel ones, IIRC.
Sig hasn't been too successful deviating from the path of producing alloy frame, milled slide, decocker equipped, hammer fired handguns.
The Sig 1911 wasn't exactly a winner in terms of volume or profitability, and the Sig 250 suffered from light primer strikes and other issues.
Glock, HK and Sig-Sauer/SigArms are all probably credibly deserving of Tier 1 in terms of their core weapons' reliability.
It's only when they deviate from their core principles that they seem to fall down.
This P290 looks like a chunky monkey the kind of thing Ruger or Beretta would put out.
I wouldn't mind trying it out, though.