Logical progression to a more demanding workout?

So, it's been a year and I am beginning to think that I should either add reformer pilates, bungee or go with a gym/weight training instead. I love the heat aspect, but my body seems to have adjusted to the intensity and I don't really get tired as I used to. Just today after thunder I felt like I've been sitting around watching tv for 15min instead of rowing at the highest intensity possible. I already asked my studio to increase the resistance, which they've done to the max. I alternate cycle, thunder and blast twice each on 130 temp so I feel like I should be getting tired after. Is this normal or am I doing something wrong? I still get pretty sweaty, but definitelly not as much as I used to initially. I am also not out of breath and don't feel like I've been working out. I am not a spring chicken and not a super athlete. Thinking of joining a traditional gym and doing some lifting instead. Any insight?