Don’t worry about this: this is how most sites on the web worked 20 years ago because PHP, classic ASP, ColdFusion, etc. didn’t buffer.
The reason people moved away from it is error handling: it was basically a cliche that you’d see an error message halfway through a page which had started out fine because there’s no way to go back and retract the HTTP 200 & start of the page which you had just sent.
The negatives you mentioned are already happening but that’s due to the widespread JavaScript culture of trying to put as much in the client side code as possible while not measuring performance except by having developers ask whether it seems fast enough on their M2 MacBook Pros with fiber connections.
> because PHP, classic ASP, ColdFusion, etc. didn’t buffer.
ASP (and I assume the others, my memory of them is more hazy) could buffer but it wasn't the default. You could control when the buffer was flushed if needed, to push initial content while something larger was being produced, heading towards the same compromise documented here (selective buffering) but from the other direction.
PHP could, too, but it required an extension which wasn’t enabled by default and had some caveats about memory use and performance way back then. I know this because I used it to implement gzip compression in PHP 3 (or maybe really early 4?) with a hook to compress each chunk before sending it, which really helped our customer’s product pages & reports with tons of repetitive HTML.
The reason people moved away from it is error handling: it was basically a cliche that you’d see an error message halfway through a page which had started out fine because there’s no way to go back and retract the HTTP 200 & start of the page which you had just sent.
The negatives you mentioned are already happening but that’s due to the widespread JavaScript culture of trying to put as much in the client side code as possible while not measuring performance except by having developers ask whether it seems fast enough on their M2 MacBook Pros with fiber connections.