The Colorado Avalanche went from being one of the worst teams in the league into a perennial playoff contender from one year to the next just off the backs of MacKinnon, Landeskog and Rantanen improvement. Players like Hughes, Hischier, Bratt, Holtz, Mercer, etc... continuing to improve is what will determine if this team is ready to compete or not, not a singular UFA signing/trade.
As for never wanting to take the next step for fear of mistakes that has nothing to do with what I said. I said the Devils should just continue to build and make smart moves. A smart move could mean a big upgrade in free agency or trade or a smaller move, my point wasn't to not bring players in but not to act desperately and let the market come to you and only make a move if you think it's worth it.