I have not talked to a single team developing mobile apps for Safari that hasn’t run into significant problems.

If you’re just building a standard body scroll website with a simple ui/ux you’ll likely be ok. As soon as you start doing complex stuff with pinned panels, or gestures, animations, drag and drop then you’ll hit the bugs.

Some of the bugs developers have been complaining about for 7 years.

Every browser we develop has bugs, Safari just has 10x as many.

I've been a web developer for about 3 years and in my anecdotal experience of the modern browsers I have had the most trouble with Safari.

Multiple times I've hit issues with things that I would have expected to be 100% complete, like SVGs not being able to properly transition animations in certain cases.

If you actually wrote a complex web application and didn't encounter significant bugs in Safari, you either didn't test very well, or your app, although "complex", doesn't try to do much.