You seem to be right that the Leafs drafting philosophy changed somewhat from focus mostly on skill to more focus placed on size in the past 3 years. One must give management credit for having the confidence to move somewhat against the trends and against the grain compared to what one is generally seeing in the NHL right now. Looking at the opening day rosters of the league (for 2016-2017), one sees Toronto already fairly high up the chart, with the 10th largest team in the league (larger than each of Pittsburgh, Nashville, Ottawa and Anaheim - the final 4 teams this year). Of note, Pittsburgh and Chicago come in at 27 and 29 in terms of league size and have accounted for 6 of the past 9 championships. Especially on defence, those 2 teams have been applauded for their d-corps exhibiting superior mobility.
This focus on mobility from the blueline seems to be echoed very often, in both the NHL circles and even in junior. If one looks at Canada's world junior selection, they also seem to be selecting based on mobility (rightly or wrongly), with the top pairing players usually possessing strong skating and puck skills (like Thomas Chabot this year, or Toronto's Morgan Rielly), a sharp contrast from Luke Schenn/Marc Staal/Keith Aulie types. This year Nashville was applauded for their strong D-core, many anointing them the best in the league, in large part due to their phenomenal mobility.
So, while Liljegren exhibits these qualities, seeing Hunter draft players like Rasanen, Gordeev, Middleton and Mattinen whose major weaknesses for the most part include skating (but strengths include size), one sees Leaf comparables likely more in line stylistically with say Mike Komisarek or Luke Schenn than say Morgan Rielly or Jake Gardiner.
From that point, larger, poorer skating blueliners seems to go against the modern trend. These trends tend to be cyclical, so it remains to be seen if Toronto is ahead or behind the curve. However, I also look at the draft and the prospect pool similar to you in that I look at the roster, analyze what is missing, and see what is coming down the pipeline to fill it (if nothing, then free agency or trades are required). Toronto has large holes on the right side of its D, and Liljegren and Rasanen both offer skill sets that few (likely none) currently in the organization offer. For that reason, I am excited for the first 2 picks and likely not familiar enough to judge or predict the long-term outcome of the rest.