Although the social situation created by the pandemic is frequently referred to as "unprecedented times", that isn't strictly true - there are a number of comparable situations in which relationships endure despite physical distance. During 'normal' times, children are sometimes separated from parents due to divorce, and some couples spend considerable lengths of time apart if one works in another country or some distance away. Family and friends sometimes end up living great distances from one another and may only see each other once per year, or even less. And 100 years ago many families worldwide were separated by a war that lasted 4 years.
Despite all these common situations in which loved ones are physically separated, relationships have endured. Parents who are apart from their children are generally encouraged by experts to keep up contact by all means possible, such as telephone calls and video calls. Those in romantic relationships usually do these things, but also send physical letters and/or gifts as well, as something tangible and a letter than can be re-read can really help to bridge some of what is lost when there is no physical contact. Considering how relationships have endured under comparable circumstances can help us deal with our own situation.
it seems like we need to be physically together to be able to touch more personal subjects
It might well be true that you find some subjects less easy to bring up when not in a person's company, and most would agree with you that what we have in the way of remote contact is no substitute for the real thing. But remember that relationships have, and continue to survive this temporary loss of contact. Even if you cannot find ways to tackle a few subjects, you have every reason to be confident that your relationships will endure with these subjects deferred to a future opportunity for discussion.
I have personally found that a combination of all available means of communication seems to have the most beneficial effect on friendships. I have a long-standing friendship that has lasted 32 years. Prior to the pandemic we would see each other at least twice a week, including having a meal together on a weekend with our families. We would also communicate throughout the week by email and text, and occasionally have a phone call. The kinds of things we would talk about varied greatly between all these mediums. Conversation over dinner with our families present tended to be about fun, trivial matters that all present would appreciate, sharing family news etc. Emails and texts tended to be about shared interests - projects we are working on separately or together, and sharing jokes that we thought the other would appreciate. Phone calls were about things that we wanted to discuss directly, but could be about serious matters or trivial.
Since the pandemic began over 12 months ago, me and my friend have spent NO physical time together whatsoever, even during the brief time last summer when restrictions in the UK eased, due to the fact my friend falls into a clinically vulnerable category. Emails, texts and phone calls have continued pretty much as normal, with some arranged video calls making up for the loss of regular meet-ups. What I have found is that discussions during our video calls are very similar in content to our lunch meetings, and everything else is as it was. It isn't the same, and we all long to have physical meetings back, but our friendship remains strong.
Anecdotally, think about how many lasting marriages took place after the First World War as a result of couples writing to each other whilst separated for 4 years. Although not everything can be addressed in a letter, evidently enough can be for a lasting relationship to form.
Based on my own experience, the ongoing advice for persons in different circumstances separated by distance, and those relationships that endured and even formed during comparable times from history, you should use every means of communication available to you with those you want to maintain relationships with. The different mediums should create different situations that lead to a variety of discussions. Physical media such as letters should not be overlooked. In most countries, delivery of mail has continued as normal, with some places 'quarantining' mail for a couple of days to ensure safety at this time.