Do I need a new MTB/Hybrid, or should I use my old one (photos)...

Hi, I've joined so that you can hopefully help me to decide what to do...

I recall the excitement of choosing a new bike back in the early 90's. I went to my local cycle shop and they showed me a nice blue Raleigh Ascender (21 1/2" frame, 26" wheels. I rode it fairy often with the kids and on UK holidays but its last outing was 2005. Since then it's sat in the garage or shed. It looks a little sad now...

So, fast forward 30 years and I see things have changed. But have they changed simply to sell us more bikes with no real benefits?

Doing a little research it seems the most relevant bike for me might be a Hybrid and I've had a look at Voodoo & Carrera but am a little bewildered by the number of models and their hierarchy.

I've stripped and DIY serviced bikes before (apart from gears) so I could clean up the old bike and see if it still suits me for gentle off-roading (no road use) on cycle paths and the like or buy a new (probably slightly used) Hybrid for up to £500 (preferably £300 used). One new innovation (to me) is hydraulic disc brakes and so if I upgrade this would be a starter spec and I'm 6'1" and 15st so I think a 20" frame (L) would be right but not sure about 29" or 27.5" wheels.

I've looked into Voodoo Bizango; Aizen; Marasa; Bantu but don't seem to be able to find an easy to read comparison table for their different models. Does anyone have a good link please?

I guess what I should do is clean up the old Raleigh, ride it, and see if I carry on riding it (to get back to fitness after lockdown laziness). But there will be likely a cost involved replacing some components, and as so many say bike technology has come on I think I'd always feel I should have something more lightweight, agile, and modern. I'm 61 now so need all the help I can get but I was also a fairly fit gym goer prior to the last year. Also, it's always nice to treat yourself to a new gadget!

If I buy something more modern, what recent makes/models have hydraulic brakes and are likely to be within my price range?

Thanks for any help or suggestions.