Given every city has it’s problems, interested to know if there are really areas we shouldn’t venture into or thru in the evenings. Admittedly older couple, very mobile.
Example a walk from Spanish Steps to hotel near Opera house Via Sistina to Via Nationale to Via Firenze is around 25 minutes. Trevi fountain less around 15 or so.
We are not planing to walk from farther places like The Vatican or Gallerie Borghese
thxs

I can say that I have never felt unsafe in Rome. Our most recent trip, this past November, we walked from our hotel near Piazza Navona to/from a restaurant across the street from the Opera in the evening with no issues whatsoever. We routinely walk 20,000+ steps a day as walking in Rome is such a great experience. We are in our 60s/70s. Of course you need to be aware of your surroundings, but we’ve never felt uncomfortable walking in Rome, even in late evening.

Depends on what you're worried about.

In general random violence is pretty rare

If you're worried about pick pockets you want to avoid crowds

Main thing is not to be distracted

Italy has one of the world's lowest intentional homicide rates
https://worldpopulationreview.com/co...ths-by-country (not fully populated)
I'd be more concerned about tripping over cobble stones and too much walking

I think it never hurts to mention your plans to your hotel and ask them if there are any streets or areas to avoid. I often find they might recommend one route over another.

You might take a look at this recent thread:
Safety in Rome