I’m also surprised this is not talked about more! I can’t be the only one running Obsidian on an older machine.
I have exactly the same performance issue. Using reading mode makes the performance a little bit better. Also turning on restricted mode doesn’t seem to make a difference, so it’s not plugin related.
I could find one other related post not yet mentioned here:
Large tables render slowly or misrender
Using the large table from that post to test performance has a terrible result and clogs Obsidian performance as a whole not just for the note.