I did a full lifting routine last summer and fall in the gym and it made a big difference. I'm still not all that strong, but I have a lot more energy and even feel younger now than I did a few years ago. I couldn't do a single pull up until like 4 months ago, so I've come pretty far but still want more.
I'll be back in the gym once the omicron bullshit dies down, but for now my main goal aside from skiing is working on my upper body, so I'm doing chin ups and diamond pushups just about every day. A simple way to add lean mass without too much fatigue. It's not quite a full lifting routine and I know I'll need to do more in the long run, but for now it works for me.
Also skiing is a lot more fun now. I used to get easily gassed and exhausted whenever I hit the slopes, especially early in the season. Not anymore.