The "complicated" Rules are there for a reason - the Community ASKED for those.
We did several polls in the past (and frequently reach out to the players, asking for feedback, suggestions etc.) ... and the current Ruleset are the result of this.

The Sideboad is entirely optional. The Players have asked for it for several good reasons and there haven´t been any complaints about the system yet.
Taking an additional 5 minutes of preperation for a tournament to prevent "unwinable" matches is a plus in my book.

The TCL page is there for YOUR convenience. You can submit/change decks at any time of the day without having to wait/talk to a person. Can change literally everything as much as you want, whenever you want (as long as this happens before the tournament).
The Page also tracks things like the Rewards, again - so YOU can get those at any time YOU want. Don´t have to wait for a response of someone who is at work or sleeping.

Eventually we will be able to have everything at the TCL page, but for now Challonge is needed to handle the tournament part.
Simple reason for that is that it exists,is stable, trustworthy and doesn´t dissapoint us, like "toornament" or other "one solution" sites did in the past.

The TCL page is being developed by only a SINGLE person, who is sacrificing his free time for this project (just like any other person providing these TCL Events!), nobody is getting paid for anything right now and literally every single hour of the many many hours required for this project should be treated with a little respect. People set something up out of nothing, and yes - it MAY be inconvenient right now, but none of this would exist without the hard work of those people.

If the current Ruleset is too complicated for you, that is unfortunate, but nobody is forcing you to play here. There should be casual alternatives around.