Russian Su-57 did not try to be a stealth fighter to kill other stealth planes

The Russian Su-57 has several major design issues (seams, rivets, wing flaps, tail, canopy) which are not optimized for stealth. The rivets and sharp edges throughout the underside shows that no effort at stealth was made.

Russia’s new fighter jet has not been built to evade radar but to counter US stealth jets like the F-35 and F-22.

The Su-57 appears to have sideways-mounted radars, it can guide missiles and score kills from that direction.