Yes both "so called pros" and DIYers are able to do good or bad work. DIY puts most things in your control so generally no surprises afterwards, you know when something is messed up.Cainvest, I never said I have no DIY knowledge or experience. What I said was I use professionals when I determine it is not worth my time to do it myself. I have done my fair share of DIYing over the years but only things that I liked to do or that I could do even if I didn't want to do them but could not afford to hire someone to do them when I was young and had less income.
I have seen a lot of DIY jobs as I suspect you also have yourself where they jobs were so obviously DIY jobs that they had to be ripped out and replaced by professionals. I had to remove and replace all the baseboards in the house we now live in. Why because the DIYer who did them, did a lousy job. Like butting two pieces at a corner instead of mitering them. I replaced them myself because I consider it an easy job to do and I enjoyed doing it. Yes, I know the satisfaction of a job well done. That doesn't mean I choose to do every job I am capable of doing though.
The end point being DIY can save you money, time and give you a quality outcome. Whether or not the time spent on the job is worthwhile is up to you.
Oddly enough, I just got back from across the street as my neighbor was having his roof done by a local guy. Got to see his (and his crew's) work first hand and did some "shop talk" with him. He's giving me a quote today.