It is not very hard to get beyond the beginner stage of strength training. Start doing any series of exercises, even with less-than-desireable technique, and if you are fairly consistent you can provide an adequate overload stimilus. After a few months of training you will likely see positive changes in your body and your strength.
Although, reaching an intermediate or an advanced levels is another story. There are several reasons why the majority of people training at your gym never even make it to the intermediate level. That is, for a female: deadlifting or squatting your body-weight, performing a pull-up unassisted, and bench pressing 100 pounds (or more than 10 body weight push-ups on the floor). Those numbers are 1.5x and 2.0x higher for lower and upper body exercises respectively for men.
1. Technique, technique, technique- It is imperative that you develop proper technique before your body can handle greater loads. It amazes me how many "active" and "fit" clients that I start working with that have no clue how to perform an exercise properly. These are not newbies to the gym, but people that have been working out for years with poor technique. It is not surprising that they don't make any progress.
2. Failing To Sure-Up Weak Links- We all have weak links that limit our performance. But part of the process of moving from a beginner to intermediate trainee is to identify and work on these weak links. It is very common to have use supplemental exercise to increase torso stability, shoulder mobility & stability, and hip mobility and stability. Just about all of my beginner trainees get a healthy dose of exercises to address these weak links. It is challenging to safely and effectively progress the bigger, compound exercises with a trainee that has so many weak links.
3. A Proper, Logical Training Program- As I mentioned earlier, it is not hard to get someone moving and make some progress. But, random exercises without an appreciation for stress, progression, adaption, and recovery will keep you from reaching the levels of an intermediate trainee. Somewhat-more sophisticated planning is important. With greater training stresses comes the need for appropriate recovery intervals. These variables, in addition to exercises selection, order, loads, volume, and tempo need to be planned in a proper intermediate training program.