There's a fundamental difference in game design theory between DotA and LoL, DotA has always been about "is that concept awesome?" before even thinking about "what is balance, what is hero role, what is skill level, etc." wheras LoL puts those things in the forefront of hero design.
There's something called radical dynamic asymmetry, one of the fundamental design differences between DotA and LoL. It is precisely due to the fact that "spells scale" that LoL is unable to create heroes that vary vastly at different points in the game. Due to the scaling on casters, it becomes far more difficult to create heroes that vary in power at differing stages in the game. As such, hero design becomes somewhat stagnant as both overall power levels and game scaling need to be comparable for heroes of similar roles.
The direct result of this, along with the lack of creativity in map design, is the constant mirroring of lane setups with match-ups between similar heroes in similar roles arrayed against each other in set lanes. This, by itself, along with the need for heroes to remain constantly similarly powered, leads to what is seen as a very stale and boring metagame of essentially the same laning phase and team composition.
While this has the advantage of making the game far simpler to understand and observe as you can quickly judge out very predictable lanes and matchups, with the game state being extremely easy to comprehend as you can directly compare heroes in the lanes or simply glance at the gold counter to see which team is ahead, this also leads to stagnation in the meta and the exacerbation of the snowball effect. If the lanes all involve similar heroes scaling in the same way lined up against a mirrored lineup that performs essentially the same way, then any advantage a team gets is transformed into a direct advantage in both laning and combat and thus can be extended to further your advantage. With such linear and consistent scaling, you are ahead once you gain an advantage with which you can very easily become further ahead.