Better be better than yesterday
Well, it's sure your body will "adapt" but the adaptation will occur only if you keep the same rhythm. I posted a ThenX cardio video before on this page, and this training has no effect on me anymore ( I do 5 sets rather easily now ). So I raised the intensity. From the "45s exercise - 15s rest" pace, I passed to the "60s exercise - 12s rest" pace. And it became pretty challenging again. To keep the same workout length, I passed from 5 to 4 sets. When it became rather easy, I replaced the first set with a set of this workout ( from 3:26 to 3:39 ):Cardio is... good to start with to lose weight surely, given proper diet you see the results fast. Problem is, after some time your body adopts to the calorie deficiency and you need to eat even fewer kcal than before, otherwise your weight will just stop dropping or even you can start gaining weight. It's a bit of a vicious circle there. Aerobic exercises are basically best to build your stamina and keep the energy levels high. For long term weight loss I would recommend anything non-aerobic, weights, intervals, etc. That keeps burning fat no matter what. Given I can barely hold my phone at my ear for 30 sec. now those exercises I cannot do.
Believe me, it's a harsh workout. They made it look easy, but I've difficulty to maintain the rhythm just after the burpees exercise. I think that if you do increase the intensity, you could still squeeze some calories out of the cardio workout. However, it's true there is a limit as you stated, and that's where you incorporate weight training.
Don't you think doing some cardio may be useful just for helping you losing some pounds even if it is on the short term ? And is your tendinitis that serious ? I mean definitively not recoverable ?