Slow is if you need to download MBs worth of JS frameworks. I love that this is usable without JS if you want to. Also the abstractions around HTML seem to be very thin so I don't really get your pint there. GraphQL seems to be a performance killer too, so maybe just use simple, boring SQL?
Downloading that all that stuff is a one time thing if you are developing. And most js dependencies are actually developer tools. The runtime dependencies of a webapp tend to be pretty minimal actually. Also, python has lots of dependencies typically.
I actually prefer Kotlin for a lot stuff people use those languages for. Similar amount of stuff to download but just a lot better tools (e.g. refactoring) and less leaky abstractions. I've used all of it of course. I just know what I prefer at this point. I was doing some python last week. It's alright but also quite a messy ecosystem.
As for Graphql, I just completed a project of ripping that out. Using it was a mistake. People like it for the wrong reasons; mostly because they are afraid of joining tables with SQL and spending some time thinking about what the optimal table structure is to minimize the amount of expensive joins needed. So they end up using stuff that does that poorly by combining the results of multiple micro-services after it comes out of the database. Which has all the predictable downsides in terms of performance. People use ORMs for the same reason. ORMs are popular for the same reason. It's not the tools but the people wielding them shying away from thinking about doing more optimal things with their databases. This stuff can work fine if you know what you are doing of course. But lots of people simply don't.
