Strength is specific. In order to become physically stronger in a meaningful way you need to train specifically. Running or other forms of endurance training are antagonistic to the building and retention of muscle mass. There are plenty of ways to get stronger, rarely are any of them bad. Finding the way that is going to build long term adherence to a program is more important than the implement used. I like a barbell because it is the most efficient way to get whole body strong, doesn't require a huge time commitment and has a very short learning curve.
Cardio improvements are very quick and lasting and do not need much more than normal life activities (provided a person is meeting the minimum guidelines for being physically active) or sport specific practice/activity. People are conditioned to believe that more is better and necessary when it comes to cardio. The truth is that activities that make you tired and sweaty offer very little lasting benefit or much of any benefit at all above your day to day cardio requirements. Excess cardio has almost zero benefits for weightloss or cardiac risk factors...things like cholesterol levels, blood pressure, heart health, plaque etc. The popular cardio fads...Zumba, cardio kick boxing, spinning/cycle studios, and now the home versions like Peloton all have very low adherence because they don't really do anything. The short term benefit is real for a sedentary person but beyond a couple weeks ..that's it.
If you surf regularly you are way beyond the minimum activity level for good physical health and you are getting plenty of both anaerobic and aerobic activity.
What strength training today does is allows you to continue to do those activities much longer and later in life at a much lower risk of injury. Waiting until you are older to begin training is like going to the gas station after you've run out of gas.
Two resources I would encourage everyone to use and explore are "pubmed" and" up to date". Both publish peer reviews studies based on actual science by experts that aren't getting paid for their opinion.