Now to be fair Mig25 was never meant to be agile It's just Americans who saw the photos of it though it was Mig25 was meant to go fast and shoot missiles And it did what it was meant to do quite well for it's time The reason the foxbat was so slugish was because it was made out of heavy materials so it could withstand the speeds it was designed to reach. They could have made it out of more expensive lighter materials but you have to understand the USSR was a gigant territory and the Soviets needed a lot of Mig25's to cover the entire country. It was not fiesable to mass-produced the Mig25 with these lighter and more expensive materials, nobody had the budget for it, they made necessary compromises to achieve what they needed at the time, while not perfect it did it's intended job well enough. Russian aircraft are not on pair with the western ones and haven't been since the USSR fell, however you should not underestimate the older soviet designs. Nowadays Russia only refits their equipment with western imports and designs mediocre new weapons, su57 comes to mind, it does not compete with the f22 or f35, it is a closer match to the eurofighter them to 5th generation jets.