I hate to be the guy who says "you're holding it wrong", but complaints like this usually indicate that a company is trying to manage their remote work the same way they did in the office, with no adjustments. Some specifics:
> People often don't perceive you as an actual human if you've only ever been a video square to them.
My remote company does regular on-sites and off-sites, which for me strikes a perfect balance between not having to deal with the headaches of an office (mostly commute and open floor plan) while still having time to meet my coworkers face-to-face.
> quick collaboration just doesn't happen anymore, or happens in a much slower and more frustrating way on Slack
Slack's huddle feature is great for the times where you need to quickly drop into collaboration mode with someone. Doing that occasionally and then structuring your work to be more parallel works very well in my experience.
> Juniors especially struggle and I watch them take many times longer to ramp up than pre-pandemic.
This is one that I actually have seen, even in my current org. I think the root of it is that going remote revealed just how much time senior engineers spend mentoring juniors by requiring that that time be scheduled. The most successful junior onboarding I've seen is when people make a conscious effort to schedule in lots of time for mentoring and training and to ensure that there's a space where juniors can get feedback quickly on Slack.
It's not that you need more time than you'd otherwise need, it's that you have to be intentional about creating the learning spaces, which doesn't come naturally to many organizations.