How is the Justice League anything like the Avengers? They are not founded the same way (BM and WW finding the others vs a spy organisation) and they don't have the same types of members (the Avengers have spies, the JL has someone young and inexperienced etc.). They don't even have the same color scheme. The only thing they have in common is that they are both team movies.
That’ about it. Like the vast, vast, vast majority of such complaints and DCEU complaints in general, it falls apart the second you apply any critical thought.