When I started Instructing average solo time was 5-10 hours, at a busy controlled airport. If a student got to 15 hours and was still not solo it was referred to the Chief Flying Instructor (CFI), generally you (the instructor) would already be speaking to the CFI prior to that if they were going past 10 hours and not looking like going solo soon. If someone got to 20 hours without solo it was extremely rare.
That being said, when I taught at a busy college, with a different syllabus of training the average solo time was 10-15 hours, this was partly because the aircraft used were a bit more twitchy and took a little longer for a new pilot to get used to, big school mentality had a little to do with it as well.
I can't see it did much harm to have a broader outlook and find my own way to some extent
The point of paying for flying instruction is so that you are guided through your training, and not finding your own way. I would take time to find a school/club where you feel welcome and your instructor has time for you, after all you are spending A LOT of money in this area. Now to be clear this does not mean leave because you don't like what your instructor is saying, as the advice may be valid, but it means your instructor should be providing adequate time to brief and debrief and answer questions.
Also remember, You don't know what you don't know... so self learning especially in the early stages can lead to some flawed assumptions that bite you later.