Discounting the above weight loss argument for a second have you ever specifically trained this limiter of “accelerations from slow speed” - workouts focusing on torque, peak power (speed/ strength) and then transition into repeating types of intervals to build your capacity? To me it sounds like you could possibly be neglecting a whole host of gains to be made in that area of your bike riding…
In relation to the S&C work I think advice from a reputable trainer whom you can get face-to-face time with is the best way to go in terms of looking at your movement and weaknesses. Essentially you’d look to start light building form and technique with even a focus on body weight exercises and gradually transition to a fully fledged S&C programme.