It was a bad contract at the time because he got paid very near the ceiling of what defencemen that don't get PP time ever get paid. If we had bridged him and he kept up his very good 2017-18 level of play for the next two years we could probably still sign him to a $5.25M AAV contract at that point. He was never going to repeat his rookie season point total as that was a consequence of getting an abnormal amount of secondary assists and getting PP time by default despite being a poor PPQB.
I don't remember how many seasons he had left until UFA when he came off his ELC, but if we had gotten him to sign a contract that included one UFA year at a pricetag below $4M AAV, then you could consider that a Nashville-tier deal at the time.
Going long-term on Skjei was not nearly as bad an idea as going long-term on Pionk this summer would be though. The guys to gamble on longer-term this summer are Buchnevich and DeAngelo.