Elastic Beatgrid Newbie looking for tips

My first major attempt at elastic beatgridding is making me wonder if my I’m approaching it right, so I’d love to hear thoughts from people who have done this a bit. 

Nearly every bar of this song seems to have a different tempo.  It seems like I need to add the “set new beat marker” feature for every bar.  Sometimes, even within the bar, the two snare hits won’t line up. 

However, the song doesn’t sound like the tempo is fluctuating so much.  It’s an old hip-hop track based on a funk loop, (EPMD, It’s My Thing) not some free-form hippie jazz piece. So I’m very puzzled by what I’m seeing on the screen with grids vs soundwaves. 

Are some songs just like this?  Do I really need to just grid this out bar by bar?  Or maybe bring it into ProTools or similar and timestretch it to a fixed tempo?  Maybe I’ve picked a really difficult song for my first try?  Or am I not understanding something? 

BTW, I’m a Recordbox newbie, but I’ve made cues & beatgrids for nearly 10 years with Traktor or Torq, and have been DJing since 1987.   After years of watching tempos drift out of Traktor’s fixed grid, I’m eager to get older songs in my library sync-friendly. I saw the Pulse tutorial (https://youtu.be/O2kS_jP0HHk), but this EPMD track seems more difficult.