Not necessarily. If you're struggling on a particular platform, it doesn't automatically mean the site is tougher or that something is wrong. Variance can make even good players feel unbeatable on one site and cursed on another over relatively small samples.
In general, though, higher stakes tend to attract stronger and more experienced players. You'll usually find more regulars, better bankroll management, and fewer obvious mistakes as you move up. That doesn't mean every player at higher stakes is great, but the average skill level is often higher.
As a novice or developing player, I'd focus less on finding the "easiest" platform and more on reviewing your results, studying key spots, and making sure you're playing within your bankroll. Sometimes what feels like a tough site is simply a downswing or a small sample size.
My advice would be to stay at stakes where you're comfortable, track your results over a large number of hands, and only move up when you're consistently winning. Moving up in stakes to escape bad results usually leads to facing tougher opponents and bigger losses.