On paper, shaheed tier drones can be upgraded with better compute to fly much more complex (i.e. close terrain hug) which exponentially drops chance to intercept by forcing defender to increase/scale IADs density/complexity. Analogy cruise missiles -> LO/stealth cruise missiles with more complex compute and flight profiles, they're still subsonic and "easy" targets when detected, but make detection hard because scaling detection = scaling more nodes i.e. Same # of munition requires #^2 sensors to detect. Another analogy is urban tag, instead of slow player screamingly loudly at fast defenders, drone is sneaking to target quietly and defenders suddenly needs more eyes for same catches, perhaps not affordably more.
IMO the _current_ problem with subsonic / shaheeds tier munitions, at least the one's being being used is they seem to have very basic navigation capabilities field by forces that don't have ability to plan better missions. VS defenders being supported by US/NATO with high end ISR that dramatically improve intercept planning/chances. Again, IMO the latter is what makes or breaks, affordable theater level shaheed spam. These are glorified mopeds + smart phones. On paper most countries can have 100,000s of them. But to use them effectively and even _more_ economically, need highend ISR+killchain to employ fraction of munitions (or some other platforms) for initial SEAD / dismantle IADs and eliminate future intercepts. AKA closer to US/PRC tier of C4ISR which will ramp into another gear once mega-constellation based. Which is out of reach for most countries, unless they strategically align to "unlock" "smarter" munitions.