I might not be the best person to comment here because I haven’t used any other platform besides MT4, and I don’t think I even will. It’s working fine for me, so I haven’t really given using another platform a thought.
It's easy and simple to use, and it has many features like server stability and can support thousands of trades simultaneously, which is why it is the most popular platform used by most traders.
The MetaTrader 4 trading platform, being the most widespread and popular trading terminal, allows you to create and use a variety of automatic and mechanical trading systems
Never thought about it, just know that most indicators are scripted for it, even the programs I wrote have been working well for me on MT4 offered by both (fxview, xtb) my brokers.
The simplicity and the nostalgia is what make MT4 much more prominent and popular. Both MT4 and MT5 are good.