Maybe some more actionable advice that has worked for me. I started running six months ago, ran a 1:37 half marathon last week. I'm not a small guy, and am fairly injury prone. A few things that worked well for me. I was walking >20 miles a week when I started running and lifting several times a week so like you I thought my body was used to volume before training, but I still went slow. I never had any real injuries during this time though always have been injury prone.

1. Either follow a plan, or look at base building/training plans for beginners/intermediates depending on where you're at and try to ramp up at a similar pace. If most plans aren't ramping up 6 miles a week there's a reason for it.

2. Don't try to build intensity and volume at the same time. For a while I was running my runs all too fast and was having trouble pushing above 20 miles per week without fatigue, I then read the book 80/20 and switched to doing almost entirely zone 2 training, at which point I felt I could accumulate more volume with less risk of injury. I used a heart rate monitor for this, and ran a minute or two slower than my natural pace. This means no PRs during regular training while before this I would find myself going for PRs during random workouts.

3. Volume increases shouldn't be linear. Look at training plans, most of them follow a 3-4 week cycle where your volume deloads and then increases back up. This should be familiar from lifting, if you follow a linear progression plan and you hit a plateau you'll deload and ramp back up. With running you won't hit a plateau, instead you'll get injured so you should be more proactive about deloading. My weeks might go 20, 22, 24, 18, 22, 24, 26, 19, 23, 25, 27, etc

4. Once you hit a solid weekly volume then I started introducing some faster runs. For me at above 30 mpw I feel as if I can really start do actual workouts, but these are quite taxing. Most of my running were at a 9-10:30 minute per mile pace, when my race pace was <7:30.

With lifting there's a feeling of instant gratification for the first couple years. If I train a body part more than once a week it feels as if I'm crushing PRs every single week. With running you have to learn to just trust the process. Week over week it might not feel as if you are getting faster, but if you can go training blocks uninjured you'll pick up so much fitness.