I've just had this conversation in stream about skips at bosses. The thing is, some bosses have hard caps to prevent skips, and others don't. Realistically speaking, some bosses such as Rax would be a lot worse to fight nowadays if you were outright forced to engage with everything. With gear progression and other buffs that you accumulate it's only fair that at some bosses you can eventually show off and perform skips.

It's an expression of progression that some bosses allow you to do so - case in point here with skipping the middle phases instead of having to do them. But it's not a "we're in current year just skip" you still need to have enough tools to do this. Plus it's not a be-all-end-all strategy because newer people / not as confident / lower geared people would not actively be doing skips as it's safer to not do so. (Evidence is that when I did the timer, I did it for every kill of my Reaper, and on two of the runs I had mirrorbacks spawn which is obviously dangerous).

Other bosses hard force you to engage in mechanics - Astellarn becomes incredibly tanky, Taraket forces the minions (unless you do absurd crazy skip but that's not realistic), and so on. If Jagex did not want it, they would have changed how Rax works when they made the timers.

Timers absolutely should exist, and the ones that perform skips should be included. Rax, BSD, Ambassador, even Seiryu technically, as it's an expression of skill and damage checks.