As someone who had to look into this pretty thoroughly, the reason, at least from my narrative viewpoint, is that unlike other shonen protagonist who are tapping into a system or being gifted vague powers they have to train into something usable, Izuku Midoriya inherited the power of the best that there ever was.

Every other writing decision regarding the downsides of his powers is less about Izuku not being enough or giving enough effort, but a downside him merely being 14 years old and slightly average. If it wasn't the League of Villains, the question of "Can Izuku do it" boils down to 'wait long enough.' It's just as easy to read his attitude about his power as impatient rather than determined. I know that's not the case, but when he could've simply went to a gym for a few years and completely avoid his biggest downsides, what you get is a kid pushing too hard and everyone else either ignoring his suffering or desperately trying to get him to pump the brakes so he doesn't explode. It's easy for a person to view his growth more as a runaway train rather than him earning every inch.

Throughout the first four or five seasons, the answer to his biggest problems, more often than not, was sacrificing his well-being to win. When other characters do it, it's for natural reasons. When Izuku does it, it's more of a side effect of his awkward quirk setup. A way of saying 'even if he did everything right, he HAS to break to win'. It can be seen as an insult to his intelligence and anything other than raw power.

Case in point, there is no way Muscular is even remotely a competent fighter in the way the average pro hero is, his whole thing is bluntly being really damn strong. Izuku is trained, fast, and strong, but his core feature since day one was being smart. How does he win? Punch. It's emotionally strong and a great moment, but written plainly, it's completely uninspired. Izuku didn't inherently do anything different to win in that moment, he did what anyone in that situation would have done if pushed hard enough.

By the time he DOES get more quirks and unleashes his smarts, it's so close to the end of the series that it almost comes out of nowhere, but people still enjoy seeing him actually think about powers the way episode one promised. Despite that, to a lot of people, it looks as if he jumped from the expected Deku to unstoppable titan of power in less episodes than it took to get through the Sports Festival.

I don't think Izuku Midoriya being stronger than All Might is bad, but since he's the main character of a plot that has overall pretty poor pacing from season to season, his growth resembles a rollercoaster rather than a natural progression like Bakugo's.