Some thoughts on all this:
1) I discovered most classic films in the pre-internet era (principally during the 80s and 90s), so by the time the internet arrived, I'd amassed substantial cinematic knowledge. Ironically, I attribute part of my success in this respect to the absence of the internet, streaming, endless channels, and so forth. More on that here.
2) Critics: My favourite growing up was the late, great Barry Norman. He was witty, erudite, and at times beautifully scathing. Like all great critics, I got to know his foibles and prejudices, and added the appropriate pinches of salt. Today, I am most partial to Mark Kermode - again making allowances for his personal prejudices.
3) Reviews: I sometimes glance at (reductive) star ratings but don't read any reviews until I've seen the film.
4) Trailers don't really feature in my decision to watch a film or otherwise, but the presence of a particular director might. Certain directors get an automatic must-see. That is never the case with actors.
5) I pay absolutely no heed to aggregated scores in imbd or Rotten Tomatoes, or their ilk. They are a surging tide of irrelevance, for some of the reasons you've touched on here. (For instance, horror films rated poorly by those who fail to appreciate the genre, or nitwit butthurt anti-Rian Johnsonites who voted 1/10 for Knives Out purely because he directed The Last Jedi). Aggregators are useless for other reasons. Take a divisive film like The Tree of Life. People tend to love or hate it, so aggregators give it an average rating. I doubt anyone's opinion of that film is that it is "average".
6) I absolutely could not give one single airborne fornication about Twatter or related social media. Utterly irrelevant to films I choose to watch, as far as I'm concerned.
7) In my case, because I write novels, all storytelling - good and bad - in instructive. The study of failure is particularly important, as it is humbling and illuminating. Therefore, whilst I wouldn't recommend others waste time on bad films, they are never a waste of time for me.