You think knowing how to build a scale is a burden? Change tuning, and see how you go.

It is a burden if you try to use it to play all the time. I do not think you are listening. The whole point is NOT to have to do it over and over again. Because you do not have enough time. And resulting fingering patterns will be very likely inefficient.
If I wanted to play in different tuning I would work out few patterns and stick to them when playing scales. But I do not - I play standard tuning - occasionally in E=>D. Very rarely E=>D, A=>G - some Baroque stuff. Or E=>D, G=>F# - Renaissance lute tunes. I do play Hawaiian Slack Key music in various open tunings but that is very much pattern based music - you learn how to execute various chord based patterns and string them - no room for single note scale type of play.

Obviously your education on the instrument is different from mine, but I honestly do know which note is where on a guitar, and I know them in relation to the key I am in. If I'm in E in standard I don't look at the 9th fret high E and think "wait, what note is that?", I don't even think it's a C# - I look at it and know "major 6th". If you practised this, in a year at most you'd do it without thinking about it.

Sorry dude but you are preaching to a choir. I did that. 25yrs ago.

The holy grail of music is to be able to think of a melody and just play it. The only way you do that is to develop a knowledge of how frets relate to the key you are in. It's a skill that can be developed, and it's not hard to do. It just takes a bit of time.

No man - that is wasteful (as far as brain cycles go). The way to play FAST (as Bruno clearly explains) you need to have "notes under your fingers" - by the time you do your computations - "ummm... I am in E so 6th is on 9th fret" you time for solo is OVER - if you really want to play fast automating certain tasks is the ONLY way.