What are the points against social engagement?

If you're asking how to integrate Buddhist values with work, having a career, I might recommend this book: The Buddha's Teachings on Prosperity: At Home, At Work, In the World, by Bhikkhu Basnagoda Rahula.

It's an anthology of the advice which the suttas give to lay people -- organised into different topics and with commentary for a modern (American) audience. Several chapters of it are relevant to the social relationships you have at work.

The Sigalovada Sutta (DN 31) is maybe the single most-detailed sutta for lay people. It describes how to tell the difference between good friends and bad friends, for example -- and warns to avoid bad friends -- but also recommends that you support good friends, family, employers, employees, teachers, and so on.

I'm tempted to add that even software development is a social activity -- that it matters what people think of you and vice versa, and how skilfully you choose and communicate with people. That wasn't the question you were asking here, but I don't think that my saying so would contradict any Buddhist doctrine.

I'm also tempted to give a meta-answer, like, "You seem to be disappointed with the result", and maybe advise about detaching from the outcome -- identify that as "craving" -- and point out that some of that unhappiness seems to be tied to "self-view", i.e. how you see yourself (e.g. "I'm Senior", and "I'm Buddhist", and "I have a master's degree and am better than the community") and so on. I don't think that's a line of thinking which Buddhism recommends, which says instead to "still their hatred" and to "settle their quarrels" (Dhp 1). However that's not what you're asking either, and I should be trying to just answer the question instead of trying to offer advice.

I don't know that Visa in particular. My guess is that it (like similar visas in other countries) is meant to be a way to give visas to people who'll make a difference to the national tech industry. I guess they're looking for founders (entrepreneurs who found companies and hire people), and/or technical experts whose work might be exploited commercially -- maybe some patents or something. I guess that very few people qualify.

I suspect that your thoughts of suing them are futile, and that it would be better for you to plan another activity that's more likely to succeed and to be beneficial -- not that I'm a lawyer, but I am twice your age, and a software developer, so more experience and I have met lawyers and government bureaucracies in the past.

Re. spiritual development rather than software development, I think that there it's recommended that you have a good teacher -- i.e. the Buddha (as a good teacher) but a good contemporary teacher too if possible. There are different schools (or sects) of Buddhism and different ways of teaching, but it includes gradual training, explaining doctrine step-by-step, some emphasis on morality and generosity (which is, I think, at least partly social).

Even when you start to practice (as a monk) I think that's not just solitary. Monks belong to a sangha. There's seclusion (e.g. from evil and distractions) but also the Kalyāṇa-mittatā as a practice or ideal. I think you're supposed to be able to learn from senior practitioners ("if I practice as they do, then I too can ..."), and so on.

The most famous sutta on that subject is I'd guess the Upaddha Sutta (SN 45.2).

There are also suttas which appear to tell of a more solitary practice; for example:

• Someone who hears the Dhamma from the Buddha, understands, and then goes away to practice -- there are several, one (maybe not the best example) is the Kuṭṭhi Sutta (Ud 5.3)

• Some solitary practice is recommended for well-taught practitioners -- there's not a lot to be said about that, perhaps, but I think it's evident that people spend a lot of time in solitary contemplation -- something like this from MN 107 perhaps:

  As soon, brahman, as he is possessed of mindfulness and clear consciousness, the Tathagata disciplines him further, saying:

  'Come you, monk, choose a remote lodging in a forest, at the root of a tree, on a mountain slope, in a glen, a hill cave, a cemetery, a woodland grove, in the open, or on a heap of straw.'

  On returning from alms-gathering after the meal, the monk sits down crosslegged, holding the back erect, having made mindfulness rise up in front of him. He, getting rid of covetousness for the world, dwells with a mind devoid of covetousness, he cleanses the mind of covetousness. Getting rid of the taint of ill-will, he dwells benevolent in mind; compassionate and merciful towards all creatures and beings, he cleanses the mind of ill-will. Getting rid of sloth and torpor, he dwells without sloth or torpor; perceiving the light, mindful and clearly conscious he cleanses the mind of sloth and torpor. Getting rid of restlessness and worry, he dwells calmly; the mind inward tranquil, he cleanses the mind of restlessness and worry. Getting rid of doubt, he dwells doubt-crossed; unperplexed as to the states that are skilled,[5] he cleanses his mind of doubt.

• One of the more famous (but atypical) suttas about solitude is the "Rhinoceros" sutta (Sn 1.3).

  I read that as saying, more especially, it's better to be a contemplative than a house-holder.

  Wikipedia says ...

  The Rhinoceros Sutra has long been identified, along with the Aṭṭhakavagga and Pārāyanavagga, as one of the earliest texts found in the Pāli Canon.[2] This identification has been reinforced by the discovery of a version in the Gandhāran Buddhist texts, the oldest Buddhist (and, indeed, Indian) manuscripts extant. There is also a Buddhist Hybrid Sanskrit version of it in the Mahāvastu. The early date for the text along with its rather unusual (within community-oriented Buddhism) approach to monastic life have led some scholars to suggest that it represents a holdover from a very early stage of Buddhism.

  ... which IMO emphasises that "usual" Buddhism is "community-oriented".

  I think it has echoes in Dhp 5, for example:

  60. Long is the night to the sleepless; long is the league to the weary. Long is worldly existence to fools who know not the Sublime Truth.

  61. Should a seeker not find a companion who is better or equal, let him resolutely pursue a solitary course; there is no fellowship with the fool.

  I read that though as saying that it's better not to be a fool, and that good fellowship is better.

I think that in practice people tend to live in mutual dependence on/with each other. And maybe the brahmaviharas are being right attitudes to have towards others in social situations.

There's a certain amount of independence taught as an ideal, e.g. if you had evil companions you should know better and act to become independent of them.

And at the right occasion or to the right audience, there's advice like "be your own refuge" and "be an island". But the more general advice is to do not only "what you know for yourself to be true" but also "what is praised by the wise".