MT4 is without question, far and away, the
worst non-web-based platform I've ever used.
It's buggy, clunky, unreliable, nasty, and it also displays many indicators incorrectly.
It's popular partly because it's the main (and sometimes the only) option offered by offshore, lightly-regulated/unregulated counterparty market-makers pretending to be brokers, who promote themselves relentlessly to very naive and gullible newbies likely to be of a gambling mentality because they're attracted by dangerously high leverage and bonus offers. Those are exactly the traders those outfits' business model depends on attracting, and they attract them very successfully.
Accordingly, MT4 is very widely used by "hobby traders" with little experience,
very little understanding, and typically wild dreams of what they can achieve and how quickly.
It's extremely unpleasant and unreliable, and has hardly changed at all for about a decade (that in itself might tell you something).
I recommend SierraChart or NinjaTrader. (Ninja has occasional problems, too, but is still in a whole different league from MT4).
I use MT4 for trading in forex because it's the most used by trader.
That fact also probably tells its own story, when you look at the overall success-rates in retail forex-trading. For some of us, that would be, if anything, an additional reason to avoid it.