I'm not sure why you bought a 250L. It really does work well for some people.
A WR250R has an OCI of 3000 miles, so compared to the others you mentioned, it's practical for a traveling bike. It's one I'm considering.
The main issue with the 250L is its weight. If it was 300 lbs wet and a little more went into its suspension, the late model version would be more appealing. The suspension can be improved after purchase, but the weight isn't easy to remove. Dropping weight should also help the engine.
I wish Cycle Trader allowed sorting by weight and engine output. That would help me eliminate many bikes. A good performing DS that's 300 lbs wet, 25 hp min, at least 200 mi range, with road going service intervals. Not much there past the WR250R.
I bought a 250L expecting so much more than it is, I wanted basically a honda WR, and the bike felt great in the showroom and on the test ride. The weight is a huge problem (110 more pounds... That's 50% more weight than the ktm... Let that sink in...) Sure the suspension can be fixed, but the rear shock has to be replaced (Which i stupidly did, and cost me $1000 for an aftermarket unit), but then you need to add power to the engine, fix the gearing, somehow drop 50+lbs, and then you have a decent dual sport.
Not much past a WR? How about a KTM 250/350 EXCF or a CRF450l? Both fantastic bikes... Honda has a 1000 mile oil change interval I believe, which is just what it is, the KTM is 15 hours, but if you're riding it normally (i.e not racing it) most people do 1000 miles or 20 hours, if riding super easy on good oil 25 hours isn't un reasonable (say fire roads and in town use) though at basically only a quart per oil change (takes less than 10 mins) on the KTM, and 1.2q on the Honda, it's not bad at all.
The CRF450L is a bit more road orientated than the KTM, but it still extremely capable off pavement, and such a good bike, just a bit heavier.