It's possible. It's not easy, and it takes a lot more self-discipline and attention to detail than when you have a teacher. I self-taught for my first 16 years playing violin and viola because, at the very beginning, I was rejected by multiple teachers and thought I wouldn't be able to find a teacher willing to accept a late starter. I actually got into a semi-pro orchestra, was principal violist of another community orchestra, and performed as a soloist with an orchestra on one occasion before I had my first lesson. But my progress was very slow for years -- I've been playing for a little over 21 years now. And when I took my first lessons, I did have bad habits that needed fixing. I sounded OK but bad bowing technique was causing me upper back pain, among other issues.

Since this February I've been taking regularly scheduled lessons for the first time, using Zoom, from a teacher who has experience with injury rehab and prevention, after two years of chronic shoulder injuries (not caused by playing) and a bad whiplash injury from a car accident last summer. I had to look online not only because of the pandemic, but also because I had been unable to find a local teacher for several years. I had some lessons in 2016, but stopped because of scheduling difficulties. I was looking for teachers who would accept adult students, could teach advanced viola repertoire, and had evening or weekend openings. There were local teachers who met every combination of two of those three criteria, but none who met all three.

As you've already noticed, feedback is extremely helpful. I started playing in orchestras very early on, and I was definitely out of my depth at first, but one thing I got out of it was pointers from more experienced players. It wasn't as much detail as a one-on-one lesson would have given me, but it was better than nothing. Many community orchestras do not audition and will accept anyone. I think what made it work for me was being willing to stay in an orchestra where I couldn't keep up at first (for many people this causes frustration), and gradually work my way up to being able to play more of the music.

Recording yourself is also helpful, especially now that we all have decent video cameras in our phones. You can watch yourself with a critical eye, and there are also online forums (such as this one) where people might be able to give you some feedback.

The thing about Simon Fischer's books is that they are reference materials. If you know what needs fixing, or if you need supplemental exercises to work on a particular technique, they can be useful even to beginners, but the catch is that you need to know what you're trying to work on. They're definitely not for stand-alone use.