How much warmth does old Atom LT lose? What should I buy to replace it?

Last December I picked up a very well-used Atom LT Jacket(2015).  The outdoorcrunch site says this jacket should be good down to 36 degrees F.  This has not been my experience as I have been cold standing around in 50-60 F.  I have also found that even a light breeze cuts through the jacket. How much warmth/insulation/wind resistance do these old jackets lose?

I am asking as I would like to replace this jacket with a new one because the fit is a little too loose and the jacket looks a little too beat up.  Maybe another Atom LT or possibly a Proton FL or Atom SL.  I am looking for something similar to the current(old) jacket in terms of warmth/breathability, so I am concerned that a new(tighter fitting) Atom LT might be too warm?

1)Planned use ~ 75% rockclimbing/belaying, 25% hiking/backpacking2)I plan to mostly use this jacket in 50 F and warmer weather (Fall in upstate NY and winter/spring in Las Vegas)3)I think I tend to run a little cold.  I plan to use this layer as active insulation while climbing and for a little extra insulation while belaying or taking a lunch break while hiking.

Thoughts?  Other mid layers you recommend?

Atom LT is not particularly warm, and fleece side panels offer no wind protection.  It should be about as warm as a fleece if wind is not in the equation.  Proton LT is much nicer jacket IMO, warmer, more wind resistant, and breathes better.  Mine has tons of use and I don't think it has lost much warmth.  I have not used proton FL.  Proton LT maybe too warm for most climbing use, would be great for belay but warm when moving.  I can only ski uphill in Proton LT if it is cold and windy, but always love pulling it on at top of skin track.

i would go for either 1) a true synthetic puffy w/ windproof exterior, or 2) a true active insulation piece such as nano air/proton. IMO, the pieces that try to do both ie the Atom LT don't breath enough to move in and aren't warm enough to use as static insulation.

as for active insulation pieces, my experience is that the lighter weights are more useful as a layer, but generally they aren't good for rock climbing or technical ice/mixed climbing because they are too delicate...

I'm a little bit amazed that anyone would ever be able to keep warm standing still in an Atom LT at 2C/36F, let alone a seven year old one.  Maybe as a reinforcement layer over base/mid/shell but on its own? Nuh-uh. And I'm not a cold guy. 

For what it's worth, I have been using mine since 2015, I have used it fairly extensively as a midlayer for sub-5C commuter cycling (and anything climbing/hiking related) but I have always needed more than just the Atom for anything standing still at those temperatures. I have been noticing a slight degeneration of its insulating capabilities over the last few years so I already invested in a slightly more modern Rab Xenon Alpine - also because these newer pieces supposedly breathe better and obviously offer better wind protection.

I’m not a huge fan of the atom LT due to the non-breathable body + fleece sides combo. Still to be cold in it at those temps probably means it was super compressed and packed away for a long time.

I’d recommend something like the nano air of proton LT as a replacement. Very breathable but pretty comfy in most temp ranges you’re describing. I can easily wear a nano air if doing anything active into the 20s and be comfy but also great piece for sitting around the campfire or colder weather cragging (or sunny lift skiing for that matter). I usually run hot enough that I only need the jacket when I stop moving but it’s breathable and quick drying enough it can easily be an always on piece too. Most versatile piece of gear I’ve ever bought 

Thanks for all the comments.

Seems like a new Atom LT would be too warm compared to my old one. Ideally, I'd like a jacket that I can mostly just keep on while climbing/belaying in 50-65 weather(not wear on the hike/approach unless super windy). Since I do run cold I am leaning towards a Proton FL.

I have an R1 that I climbed with last winter/spring(las vegas). But this never felt quite right. AS I would either climb into the sun and get hot or climb into the wind/shade and get cold.

Any thoughts/advice on how the Proton FL compares to R1?

If you are looking for a potential alternative to the arcteryx lineup Patagonia has the DAS Light hoody. Used it in vegas this past winter/spring as an outer layer and it stood up to the wind and abrasion fairly well. I normally climb in the r1 hoody so the layer on top was quite nice for the belays and its fairly light in my opinion.

Also same with everyone else on the Atom LT, it doesn't seem to work well as a standalone against the cold unless you are really active. Looks super fashionable over the patagonia stuff though lol.

If you want durable synthetic insulation, continuous filament (climashield apex, arctyrx coreloft continuous) is much more durable than short staple (primaloft, arctyrx coreloft compact).

My experience has been that primaloft gold gets noticeably packed out (still usable, just less warm) after ~100 days of abuse, and apex takes ~300 days to get to the same point.