For a lot of us working to decouple diet culture from fitness, the measure of a "successful" workout routine historically translated into how many pounds or inches were lost, or how differently your clothes fit. Below are a few metrics to focus on instead that are outside of weight loss and body changes, when it comes to how successful your current routine is.
But first things first, it's important to clarify what a "successful workout routine" means for you, and you only. For some, increasing strength may be a goal, and this can be achieved by applying progressive overload, and working toward completing more reps or lifting more weight during a particular exercise. Especially when you have been accustomed to using exercise purely as a method to change the way you look, training for athletics rather than aesthetics can be a helpful shift to make.
However, I would actually recommend not basing the success of your workout program solely on how it improves your performance: because just like you may have been attributing your self-worth in the past to how much weight you can lose, it's common to then begin attributing your self-worth to how much weight you can lift, instead.
You don't need to be regularly smashing new PRs in order for your workout routine to be successful - this is why progress and success shouldn't just mean better, faster, or stronger. Actually, it's preferable to widen the criteria for what makes your program successful outside of how it improves performance because eventually we WILL max out on our genetic potential for strength, speed, endurance, etc, anyway.
And for a lot of people who are moving their bodies or reasons other than changing them, and are conscientious of not letting the pursuit of athletics become as obsessive as the pursuit of aesthetics, progress and success can instead look like:
taking guilt-free rest days
being able to eat previously "off-limits" foods after a workout
giving yourself permission to explore different passions other than fitness
enjoying a workout regardless if you PR'd or not
or even being ok with exercising less
I believe hitting any of the above metrics would mean the routine you're doing is incredible successful, and would cheer you on for your accomplishment!