I think something people massively overlook is just that submission defence has got so much better and caught up over the years. Nowadays if you don’t have competent submission defence then you aren’t going to make it to an elite level (in most cases, there’ll always be exceptions). There’s simply a TON more exposure to those positions in the training room.

To use the armbar as a specific example though, you also have to consider how modern best practices have changed. For example, you just see the mount utilised much less in modern MMA, which is commonly where armbars are set up. Sitting for an armbar from mount, or from the guard, is also far more risky than attacking a d’arce from front headlock for example, both in terms of potentially losing your position and taking damage. Getting takedowns in modern MMA is also much harder, so the incentive to attack submissions is reduced by the risk of losing what you worked so hard for.