People whinge about modern tech being too complicated but have never really taken the time to experience and understand it - they just assume it is and come up with utter garbage muttering "marketing" etc. But it isn't any more complicated at all and often actually easier to maintain.
For example: Di2 and eTap are easier to adjust than mechanical because they allow for electronic micro-adjusting. I can simply hold a button on my eTap brake levers and micro-adjust if necessary whilst riding.
Changing brake pads for a disc braked bike is no more difficult than for a rim braked bike.
Swopping cassettes, chains etc are easy too. Chains now have 'powerlinks' etc which make installation even easier than before.
Tubeless? Easy. Trick? After installing the rim tape properly, not allowing any gaps, put the tyre on the rim and run a tyre lever halfway on one side to partially seat it onto the edge of the rim. Repeat on the opposite side. Do this and you can inflate the tyre without the need of a compressor./ Airsoft etc and leaks from not putting in sufficient air to seat the tyre properly is avoided. I've got 5 pairs of tubeless wheels, all done myself, all no hassle at all.
I use Park Tools including their repair stand and can highly recommend them (plus their videos as mentioned by another Poster above if you need help) but there are many alternatives. With the correct tools, all bicycle-related work is not difficult at all. Keep a bike in good order and none of the problems an incorrectly maintained bike will throw up such as seized components etc will be an issue.
Well the OP posit is/was that "[Despite some . . believing that a bicycle is a hugely complicated machine . . . I assure you that it is . . . quite simple."
"modern tech . . . isn't any more complicated" Is this your rational belief?
You are introducing the "TOO" complicated assertion.
Is electronic shifting "complicated"? Well it's certainly
more complicated than mechanical.
A hydraulic braking system is
prima facie more complicated, compared to one operated by cables (either disc or rim) (TRP Spyres ftw)
Noone has suggested that "Swopping (sic) cassettes, chains" is complicated or difficult: strawman
Is installing a tubeless tyre complicated? Well, if installing one with a tube is easy then tubeless is harder and takes longer(investment of time). Does allow a
tyre insert though, which I can't use with a tube.
Since the OP didn't want to play/chat, do you think internal cabling and pressfit bottom brackets are more or less complicated than the technology they replaced? Have you replaced 'cartridge' bearings in your hubs? Did you find that easier or more complicated than cup and cone? Bonus question: did you enjoy maintaining cottered cranks?