I have read a lot of good things about the WLToys 1/18 cars. Lots of different "cars" on the same platform, and lots of aluminum /steel upgrades... There is the "Standard" version with a 390 brushed motor, and the "B" version with a 540(!) brushed motor.
390 version -
https://www.banggood.com/Wltoys-A97...mds=detail-left-hotproducts&cur_warehouse=USA
540 version -
https://www.banggood.com/WLtoys-A97...-1044136.html?rmmds=category&cur_warehouse=CN
Parts / upgrades -
https://www.banggood.com/search/a979.html
I also have the Revell Modzilla - but the Sandyland version. My kids loved it, but yeah, I had issues with it.
I also have the Hobbyking 1/16 SCT and 1/16 Mini Monster truck. The SCT was a bag of issue, took me about a year to get it running reliable. The MMT is more solid, but still not 100%. Still, there are upgrades available. a 380 burshed motor would make it great for a small kid, and there is a truck and a bug version, RTR, ARR, and Kits.
https://hobbyking.com/en_us/basher-hellseeker-rtr.html
Most of my MMT issues have been with the outer suspension pins popping out of the hub carrier / a-arm. I think I will go aluminum for this part soon... The MMT does have great diffs - sintered steel. I have actually mod'ed my mini-sct to use the MMT diffs. They are solid. the stock SCT diffs were butter.
HK also has some 1/18 trucks, but I have heard no good news about them, so I have stayed away.