Your mouth still works & your hands…

You have so many other options to have fun, then regular vanilla sex. Have you ever tried prostate TLC? Goddess Worship? I have lots of creative fun options that come to mind….

But to answer your question, while I don't have too much trouble getting an erection (Thanks to Viagra) I often engage in pleasant activities with gals that don't require that I have one.

 
My favorite being mutual massage.

 
Performing oral sex on her is also a perennial favorite.

 
Then, of course, there is the sublime enjoyment of company and conversation which I highly desire with many of these gals.

 
As for you not getting an erection with a gal you're not into, that's just your mind telling your body:  "ude, let's blow this joint and find something better to do."

 
Wise advice.

I know many older gents who don’t get hard but still experience pleasure.  Even to the point of getting to orgasm during bbbj despite never reaching a full erection. Some will prefer a hj finish. Some don’t ejaculate, but may still experience orgasm, others may just appreciate their sensations along the way.  All are enjoying their experiences.  

If this is your scenario, then by all means keep hobbying as long as it suits you.   If you aren’t feeling anything though, might be time to reconsider your approach.

As for me or maybe "we" get older visual stimulation is kinda key along with a good attitude. If you ain't feeling it then that will fuck with your mind.
There's some ladies that because I'm into them can get me off the minute I walk in the door.
So to your question, "Any old guys still hobby when can no longer get it up good"....answer is "No"

Get a provider who has experience with giving a prostrate massage , I guarantee you will pop.  Very few providers are good at it so check reviews closely. Once you experience cuming that way a time or two it will help you to get your confidence back. Some providers offer the service but don't advertise it. Extremely great hygiene and being very polite helps open the door.