By the way, does anyone knows what is the output power of 30N6's transmitter? Looks like this data is still classified, I was unable to find it. Only for S-300V's 9S32 radar data is available, but from highly unreliable source. It states an average power of only 13 kilowatts and peak - of just 150. With that, it won't be able to track stealthy targets at distances beyond 25-30 km at best, so I highly doubt it.
As the main question was concerning Stealth vs modern SAMs (S-300P/Patriot)
In the '70s during the development of these fundamentally-new, digitally controlled phase-arrayed, multi channel SAM systems were aimed to counter Jamming, ARM's, and Weasels.
The AN/MPQ-53 and 30N6 (Flap Lid of SA-10) designs answered these challenges, by significantly reducing transmitted power (negating side/back-lobe HARM shots), and narrowed down monopulse pencil-beams (disabling track breaking efforts).
When the Stealth appeared, during the '80s, both system (Patriot/S-300P) fire control radars needed a major redesign, to counter these new threat effectively.
The Patriot PAC-3 system received the AN/MPQ-65 set, while the S-300PM received the (Tomb Stone SA-20) fire control radar.
My educated guess is that...
Patriot PAC-1 and PAC-2
S-300PT (SA-10A) and S-300PS/PMU (SA-10B)
... has limited capability against Stealth, as they were designed against (TBM's, ECM, ARM's,and Weasels).
While on the other side...
S-300PM/PMU1 (SA-20A) and S-300PMU2 (SA-20B) and S-400 (SA-21)
... is ready to meet the Stealth challenge.
(as they are designed to counter it)
ps: just like a speed bump...