As a solo traveler - I always get it on any day that I'm there for the full day.
I was a WDW AP for most of the 2010s. My first couple of trips to DLR, I would do what you're describing - just focus on the DL-specific rides. I eventually stopped doing that - I realized how much more immersive the experience was if I tried to ride as much as possible, since most of the attractions aren't pure clones of each other.
Many rides at DLR don't have G+, so you'll have to wait in line for those. If anything, G+ will save you the wait time for the headliners, which will give you more time to experience more of the parks, including the rides that you might instinctively skip.
Like, for me, I would never ride Tomorrowland Speedway at WDW. But, one night, I grabbed an Autopia LL for five minutes ahead, and it was pretty fun, and a different experience - unlike WDW, it goes through the woods and under the monorail (which is not particularly high off the ground). Not a first choice ride for me personally, but the experience was worth it - and I would never have waited in line for that.
The main G+ lure for me is the chance to ride my favorite stuff multiple times, especially so that I can time certain ones. For example, Thunder Mountain will have a pretty short line if you ride it in the morning. But a night ride is that much better than the morning ride - and that's the time of day that the park will be much busier and the line a lot longer. (I'll save that LL to use that timeframe.) I also prefer Guardians to DHS's Tower of Terror, and Guardians has six different songs/rides - I'll gladly take the chance to get an additional ride each day without the 75-minute wait.
G+ also gives you a potential side benefit - if it happens that one of your LLs gets cancelled, the replacement multi-experience LL will work at non-G+ rides. (There's a whole strategy around fishing for ME LLs, which might or might not be worth your time - but I was able to ride Alice and the Subs one night within a half-hour span using ME LLs because Buzz was down but they were still offering LLs for it.)
I would at least try it once - I think you'll find it worth it.