Based on the amount of timeskips that mentioned 'a few months later', it's probably already been more than a year since he developed new techniques. I guess authors is wary of making MC too overpowered but that's a bit odd, since he allegedly already is. And considering his character, filling up his arsenal should be top priority. Doesn't make a lot of sense.
I guess improvising half-baked solutions to the roadblocks he always ends up facing, is what makes the story for some people but that quickly gets boring.
The team rocket from temu starting to be more interesting than MC's gang is quite telling.
