"I think Google Ads should be simpler to use (dumb it down), should be more transparent with its costs and bids, and should offer more options to control ad appearance"
Firstly, more options won't simplify most likely.
Secondly google has been 'simplifying' for a long time, to their advantage. Increasingly Google push people down the performance/CPA path saying our smart systems will get you the best results 'believe us we're Google' but it's mostly not true. The best results are often from a manual as possible campaign and they make this an ever harder option to take. There needs to be far better regulation here.
Marketing is one of those skills where art meets science. If you let the algorithms take over they'll often look good at a base metric but as soon as you dig around you find you're sacrificing wider goals or mostly getting sales you would have anyway, or paying crazy amounts to finish off the budget type etc.
Google is a great advertising platform, but adding your money, limited controls and trusting google systems to work it out is a horrible way, and something I see all too often. I suspect it's largely because you can spend an < an hour setting the easy way, or spend a day or more setting up a well researched and manual way, but on both client/agency side people don't want to spend the time/money getting foundations right, or simply have the time or aptitude.
I say the best thing is for some regulator body to go over the system changes over the years and ask why features plus analytics were removed, hidden or changed and put rules about these controls and ongoing changes to live up to the level playing field tenent of good capitalism. Maybe it is happening somewhere but I haven't seen it, and it is long overdue.