I hear this a lot, but the thing is you could say this about any profession, and in fact there's a good case to make that politics gives people a wider range of experience than most careers.
For example I went straight from university into civil engineering. This widely regarded as a 'practical' profession, but I must admit it's a very limited form of practicality. It's taught me a lot about foundation bearing capacity and tunnel linings and numerical modelling and construction contracts but I couldn't honestly say it's given me a particularly wide understanding about 'how the world works'. My career hasn't given me any insight about foreign policy or how the NHS works or the financing of council housing or the opportunities and risks of AI.
Councillors and MPs meanwhile get experience in all sorts of issues through case work and the huge variety of issues that appear on their plate. Of course some of them will do next to nothing and just blag their way through it - but that's due to personal laziness, not an inherent problem with going straight into politics. There is something to be said for having a 'hinterland' and non-political work experience, but looking at the efficacy of senior politicians, there's no clear correspondence between who has done a good job and who has had significant experience outside politics.
I think it's a bit different though. We don't expect civil engineers to represent our interests and make national policy based on it.
We do expect politicians to broadly represent our interests. While in theory there is nothing stopping politicians from canvassing opinions and representing those in Parliament, it is not really a substitute for having actually experienced these things. Obviously no politician can first-hand experience every issue, but with 650 MPs having worked in a variety of professions, you should get a broad range of experience of non-political working life.
If we take Streeting as an example, he has only ever worked in politics. First it was a students' union, then the NUS, then Labour. All three of these organisations are quite odd because they're tightly coordinated political organisations where to get to the top job (as Streeting has), you just need to perfect politics and the machine, but nothing else. That's not really a highly-valuable skill in a prime minister, bar the fact that they are likely to be good at international relations.
I have the same criticisms of Burnham in the by-election.
I imagine your experience as a civil engineer has given you insight into things like working conditions, worker satisfaction, planning policy, archaeology discovery difficulties, building regulations, etc. If you combine that with an MP who has worked in cybersecurity and another who has worked in accounting and another who has worked as a GP, etc, suddenly you get a representative house.