So my tuppence worth for the plethora of views already here:
Yes no chill is certainly possible, many people will attest to brewing effectively without it and rarely if ever having problems.
DMS in passively cooled beer will be higher, that's been evidenced and is inevitable. Whether it will reach taste threshold when using highly modified malts is going to depend on the ingredients used, length of and vigour of brew, and duration of cooling.
The risk of bacterial contamination is inevitably higher. Sweet fresh wort is a near ideal culture medium for micro-organisms, that is sort of the point of making it since it's good for growing yeast in. It's also great for growing bacteria. There are always some bacteria in the environment and 100% sterility outside of a lab environment is going to be impossible. Whether the bacterial growth will ultimately outpace the yeast after pitching is going to depend on lots of issues including air exposure, sanitation of items in contact, multiple handling of the wort, oxygen, OG, time, temperature and other environmental factors. This is an undeniable risk and it's a lottery each time if the beer will spoil.
Chilling fast does not eliminate the bacterial contamination and spoilage by any manner or means, it does though reduce the risk, bacteria thrive at a higher temperature than yeast which makes the race to colonise the wort advantages to the yeast if your wort is cool.
Chilling doesn't require the ground water to be cold, put two chillers in series, one in an old FV filled with water and a whole big chunk of ice or ice pack. I've just started doing this and it cooled the wort through two immersion chillers deliciously quickly - no I didn't time it sorry.
Hot side oxidation does happen, it's another risk, yes it can be minimised by cubing and eliminating oxygen, but it's an undeniable risk.
Time. Active chilling will reduce the handling time and you can get on with other things. I clean up my kit while the chiller is running which I'd have to do anyway so it's a win win.
So each to their own. Personally if I'm going to invest my time (and money) on ingredients and a day brewing, the last thing I'm on for is messing up a beer because I didn't chill it quickly enough. It's risk mitigation not elimination but then again so is wearing a seatbelt, getting a flu vaccine, wearing a face covering, not standing near cliff edges and making sure chicken is cooked through!
Anna