Folks, training to achieve expectations may vary among folks.
If you have to stop and think about it (some manipulation), your conscious attention is being diverted away from whatever else is happening. I've always thought that for my needs, it needs to be first nature. Second Nature may be 'good enough for government work', but only having some manipulative skill become second nature isn't my preference. It needs to be First Nature. It needs to happen without having to divert conscious thinking to the task.
FWIW, the same sort of disadvantage of having to manipulate a manual safety used to be said by folks who thought having a safety strap or thumb break on a holster might get them killed. Well, then along came the LIII holsters, swivel hoods, middle finger switches, etc. Gear got more complex. It happens.
Manual safeties still exist on long guns used in LE/Gov/Mil. For a reason. Human nature and fallibility can produce occasional unwanted consequences. Training (and policy) can be geared to address concerns about such things.
There are two disadvantages in manual safeties. One is the reick of failure to disengage, the saaftery and the second is the time rquired to manipulate it, which could be extremely important.
These only materialize with firearms that require an operation separate and distinct from that which would be done if there were no safery. With a 1911, the shooter's thumb will be put on the safety anyway, automatically. With an XD or a Smith and Wessson EZ, simply gripping the gun disengages the gip saftey automatically.