Power certainly isn't special in this regard, but the Sox were an awful power team last year, so it's something that stood out for the 2017 team.
While I'll concede that the actual results don't show much, I would quibble with the idea that a team that is 26th in SLG and 12th in OBP would reliably be the 6th best scoring team in the AL (10th in the majors). Yes, they were a good base running team and that likely helped them to outpace their expected run production, but that can't account for all of the difference.
I'd wager that if you ran the season 100 times, they end up 6th in the AL (or better) in a small fraction of those simulations. And that production was likely aided by facing weaker pitching staffs. I'll have to see if I can dig up runs scored vs individual pitchers and can compile some totals.
I would take that wager in a heartbeat if you ran that based on their projected opening day roster. Because they were 26th in SLG and 12th in OBP due largely to the fact that they had 5 regulars (Moreland, Pedroia, Bogaerts, Bradley, Ramirez) and their top 2 utility players (Holt and Hernandez) who either missed significant time or played through injury. Every team has injuries. But that was a) a bit more than expected (this is my perception) and b) mismanged by the coaching/FO staff in a way that has hopefully been identified and won't be repeated. They also had a black hole at 3B for half the season which has ostensibly been filled. Even so, their .736 OPS (11th in the AL) was only .014 lower than the 6th best AL team and MLB average.** There's no arguing this isn't a team built on power. And they could use a power bat. But they're a middle of the road AL offense at worst.
The Astros bludgeoned Red Sox pitching in the ALDS. I think it's a fair assumption to make that playoff pitching staffs are better than what teams face in the regular season (hence the argument about beating up on weaker teams throughout the season). Ours was not, and that was the biggest problem with the 2017 playoff performance. The Astros hit more HR (2 HR/G) and scored more R (6 R/G) against our playoff pitching staff than what they averaged through 162 G (1.5 and 5.5) while padding those stats against weak staffs. But in the 14 playoff games they played against the Yankees and Dodgers, those numbers were 1.4 HR/G and 3.9 R/G. The Yankees were 1.2 HR/G and 3.9 R/G in their 13 games. Comparatively, the Red Sox hit 1.3 HR/G and scored 4.5 R/G in the ALDS. The Astros' high-power(ed) offense did not lead them to a World Series title. It did help them breeze through the ALDS against a weak pitching staff. I don't think there's a larger conclusion to be drawn from this about whether having an elite offense is necessary to win in the playoffs, especially because of sample sizes, but it does go against the perception that the Astros' powerful offense led them to a ring (ergo the Red Sox need an elite offense or they can't compete).
Their two largest problems as I see them: 1) They need their ace starting rotation to pitch as such in the post-season. The 2017 (and 2018) Sox were supposed to be built around 3 CY-caliber starters. One was hurt, another faded, and the third was just not good in 2017. 2) In 2017, they paid $105 M to their 5 highest-paid players (Price, Ramirez, Porcello, Sandoval, Pedroia) and got 1.2 fWAR in return. If they're not getting much more than replacement-level performance from that portion of the roster, it's hard to be successful in the long term. Sandoval is obviously gone and a sunk cost. Pedroia is still a 2-3 win player going forward for as long as he can stay on the field. The other 3 (and any other big dollar FAs that may come along) have to either perform or be replaced without eating their entire contracts in order for the team to be any more successful than 2017 over the next few years. We've seen the variability that exists in a roster over the last couple years. That's not going to stop. Maybe guys like X, JBJ, MM, Beni, Devers, Betts improve over last year, and maybe they don't. I don't believe they're the key to outperforming 2017's end result. It's the guys you pay big money to for their track record of performance that have to sustain that through the majority of their contracts. Otherwise, it's a never-ending battle of trying to plug holes with low-cost options - an undesirable place to be for a team with a large payroll and thin farm system.
** -- I'm curious, does anybody know if/where preseason team batting projections can be found? I.e. without having to go through player by player, what were the 2017 Red Sox team OPS, HR, or runs scored projected to look like? 2018?