Yes, geometry for shorter riders is one of the reasons that bikes with 27.5" wheels are gaining in popularity.

26" wheel MTBs worked great for shorter riders. 29" wheel MTBs work great for many riders, but those tall wheels can make for weird geometry on small frames.

However, although you could swap your 29" wheels for 27.5" ones, that would drop your whole frame 19 mm (assuming same tire width). Lowering your frame would improve the clearance at the top tube, but it would decrease the clearance at the crank arms and it would affect handling.

Looks like you have about 1.5" tires on your 29" wheels currently. If you went with slightly wider tires on 27.5" rims, that would lower the frame a bit -- hopefully the "just right" amount.
WTB Horizon tires are a good choice in 27.5 x 47 mm; they also offer a Byway model with a little more tread. And there are lots of choices in 2" (~50-55 mm) width for 27.5".

Next time you go to your Local Bike Shop, maybe ask if they have any MTBs with 27.5 wheels on them, and then ask nicely to see if you can swap wheels and try it out. An offering of beer to the shop may help with this request.


However, if you can't comfortably straddle the top tube on your bike as it came from the shop, then you bought a frame that is too large. And I agree that the 29" wheel size may have contributed to that size problem.