There's definitely a multipurpose aspect to a lot of older martial arts styles, where they are no longer tested for their fitness in most practical senses, and

There's definitely a multipurpose aspect to a lot of older martial arts styles, where they are no longer tested for their fitness in most practical senses, and so the form gradually degrades into purely being sport or performance. But the other side of that coin is that arts that develop a restricted kind of technique often do renew themselves when they are reintegrated into a practical system by someone with some design sense, and sport styles in particular allow subsets of fighting to be explored in depth and remain vibrant through competition, even if they are not "realistic". Boxing, for example, is hugely restricted to avoid grappling and yet the fighters still try to clench up regularly. Actually staying on your feet, throwing punch after punch, is hugely unnatural. But boxers that learn enough grappling to escape submissions can cross over to MMA and do respectably well, because they have the skills to bring down someone at a distance. Judo, likewise, is full of artifice these days. There are mamy restrictions on the types of holds, penalties to avoid stalling, scoring balanced heavily towards getting off an impressive throw, and a limit of up to twenty seconds to get a pin. But these restrictions also compel judo players to develop strategies for a quick, confident takedown and submission. The styles that suffer, in contrast, are the ones that may have had relevance in the context of weapon fighting but are now mostly performance - the tai chis or aikidos of the world. Krav maga persists in part because its design works with the smaller knives that modern armed forces continue to use. Ultimately, the point of training any named techniques is to develop muscle memory - what that memory is used for is secondary, and in that sense all popular systems succeed.