The issue with flash and applets was not that you had to download stuff.
It was that the security was non-existent (leading to the embedded runtime routinely crashing your browser), the interactivity was divergent from its surroundings, and the accessibility model was MIA.
Also downloading 500K over 56k and over fiber or 5G are rather different propositions.
Isn't this like a revival of the dreadful era of browser plug-ins from Adobe Flash Player to Java applets?