It's the opposite. Offense generally can't be taught. Defense, anyone can learn.
That comes with two caveats.
First of all, offense is rarely a byproduct of one single player, but rather the way the puck (or ball) is moved around to create looks. A good question to illustrate this would be would you rather be the coach of the best 3 point shooting team in the NBA, or the best 2 point FG shooting team in the NBA? For me, it is always the latter, b/c while good 3 point shooting is nice, you know that you are taking high-risk, high-reward type shots b/c you struggle to move the ball well enough to get good looks inside. Whereas being a coach on a team with good 2 point FG percentage means that you are probably getting a lot of points close in and moving people around so that you have a mix of very high quality shots within a certain radius of the rim. Similarly, while players like Crosby, Matthews or McDavid have offensive skill, their skills drive some play, but they are also not the sole person behind the creation of offense either - it is how your team spreads the defense around and gets into situations where the defense gets out of position and you can force odd-man situations in limited space (think how many times last year we would get 4 players on one side of the ice and out of position, so that the team would be open to 2 on 1 situations.
The second caveat is that while anyone can learn defense, if you don't maintain good defensive play, you won't make it at the highest level. Same way I can teach someone how to change their car's oil, throw a football, or any other item that can be taught, if the person being taught does not maintain what was taught, then it won't matter what happens.
It's no surprise why the teams who typically finish at the top get stellar defensive play. Washington was average in GAA during the regular season (2.90 GAA per game). That improved to 2.54 GAA in the playoffs. Vegas was at 2.74 GAA per game in the regular season and improved to 2.35 GAA in playoffs. Vegas actually reduced their GF in the playoffs vs regular season (3.27 GFA in regular season vs. 2.85 GFA in playoffs).
Columbus, Boston, Washington, and Pittsburgh were the only teams who increased their offensive output per game vs the regular season (SJ was flat 3.1 regular season vs 3.00 in playoffs). On average those 5 teams (SJ included) averaged 12.8 games played in the playoffs, total.
Teams that decreased their GAA from regular season: Washington, Pittsburgh, Winnipeg, San Jose, Tampa Bay, Vegas, and LA. For the 7 teams that decreased their GAA from regular season to playoffs, they averaged playing in 14.9 games played in the playoffs, total.
If you are going to survive the playoffs, defense is more important than offense....