In my opinion Finland was eliminated due to a number of issues, not just bad goaltending, or defending, or offense. None of them were overly bad, it was just that none of them were great either. If just one of the issues hadn't been there, it wouldn've been an easier time to finish top 4, or get a medal. But when they all happened simultaneously, this is the end-result.
Defense was overall decent - gave up more shots (130) than the other big nations, but not significantly so. Though it struck odd to me that a lot of them were high-quality chances, with opposing forwards left undefended in the slot or unhindered due to lack of physical play.
That also carries over to goaltending, Luukkonen wasn't great, he was slow and out of position at times, but he wasn't abysmal either, and a lot of it came down to the opponent getting easy shots from the slot. I've a feeling that if those hadn't happened, people wouldn't even complain about him. Still, would've wanted a look at Lehtinen, if for no other reason than to light a fire under Luukkonen.
Offense underperformed, but again it felt like it was due to lack of physicality. Finland generated a lot of shots (210, as many as Canada has generated with 5GP) but they often came from outside the slot, at the end of an attack when the puck-carrier was trying to get a rebound but noone was there to pick it up. Of course there was also the issues with finishing, with Tolvanen and Juolevi combining for 50 SOG and 2 goals - but you need world-class finishing anyway to score from those low-quality, outside the slot shots, and neither Juolevi or Tolvanen is known for that.
Overall it was an underwhelming effort. Part game plan's fault, part players' fault, part just poor luck.