With your training have been focused on long steady state aerobic training it is no wonder that your strength and agility has suffered. Our bodies get really good at the things we do the most and you have spent a prodigious amount of time in your training. We do not address plyometrics because this is not an important training method for mountaineers and alpinists. Without adequate strength and coaching it is a very good way for the inexperienced to get injured however. Other than making dynamic moves on hard rock climbs I can not think of time in my life time when I need to have explosive strength (like pylos are used to develop) in an alpine or mountaineering scenario.
I suspect that agility is a bigger issue than explosive power. Your training has either been seated on a machine (bike), supported in water or running on pavement. In all of these the movement pattern is strictly in the sagittal plane and every pedal stroke, every swim stroke and every running stride is virtually identical. Trail running and good mountain mobility requires dealing with changing foot strikes and more lateral (frontal plane) movements. There is a special sort of reactive strength, balance and agility needed to move efficiently over rough terrain. We’ve tried, but never found a way to train this outside of a mountain environment. You have to spend many hours on rough terrain. This might range from rough/rocky trails to talus slopes to 3rd class scrambling.